Why Are Runners So Aggressive Against Matt Wallner's 99th-Percentile Arm?

[Matthew Lenz]

The very Minnesotan outfielder has a legitimate cannon attached to his right shoulder, yet baserunners attempt to take extra bases against him at the third-highest rate (advance attempt rate) of all outfielders. One diminutive teammate, meanwhile, had the second-weakest arm at the position in 2024, yet tied for the lowest advance attempt rate. Make it make sense!

Image courtesy of © Jesse Johnson-Imagn Images

It would be natural to assume a strong correlation between the strength of an outfielder's arm and the advance attempt rate against that defender. That is to say, we might assume that the stronger the outfield arm, the more conservative baserunners will be. However, while that might prove mostly true, Matt Wallner and Manuel Margot are counterexamples, reminding us that there is more to throwing runners out than having a Howitzer.

As Wallner looks to be the heir apparent to Max Kepler in right field, I felt it would be worthwhile to look at what might be the reason for this discrepancy. Naturally, my first thought was to consider the accuracy of his throws.

Arm Accuracy
This isn't quantified publicly (yet), so I put on my amateur scouting goggles, watched a few dozen plays, and found nine where Wallner was attempting to throw out an advancing base runner. Of those nine, I determined that six of those were inaccurate throws. That's not to say that the runner would have been out had the throw been better, but it is to say that Wallner made a legitimate attempt to throw out a runner and the throw was off-line. Maybe I was too harsh, but even if the throw was simply on the wrong side of the bag (like this one), I deemed it inaccurate. To be fair, I don’t have a good idea of what percentage of outfield throws are accurate, but my gut tells me that it’s better than 33.3% for some of the best arms in the game.

Regardless, this subjective analysis alone wasn’t enough to make a strong conclusion on why runners are particularly aggressive against Wallner. One thing that did stand out as I was reviewing all the videos was the number of times Wallner was close to catching a ball hit over his head but just missed, like in the highlight below. This led me to another important aspect of throwing as a fielder, which is how you approach the ball.

Approach
While I initially noticed this when reviewing videos for arm accuracy, the way he approaches a ball is something Baseball Savant has quantified. First, I looked at his starting position relative to the rest of the league, in case he’s positioning himself differently than most of his counterparts. Alas, on average right fielders positioned themselves 295 feet away from home plate, while Wallner averaged 293. That’s pretty negligible. Then, I moved on to what happens after the ball is hit. That’s when things started to make more sense.

Wallner’s Outs Above Average (OAA) was -3 in 2024, and he covered nearly four fewer feet on batted balls than did the average right fielder, which put him tied for last with Yordan Alvarez. Digging a little deeper, Baseball Savant breaks apart an outfielder's jump into three areas: reaction, burst, and route. What you find is that, while Wallner’s routes are considered a strength, his reaction and burst times are considerably below average (his data point is directly to the left of the brim of his hat in the picture below).

Not only does this impact his ability to catch baseballs, but it impacts his ability to approach the ball in a way that is going to set him up for a good throw. In fact, more often than not, the most direct route to a baseball (remember, that’s his strength as a fielder) is not the best way to approach a baseball to set yourself up for a throw. Instead, you often want to take an indirect route so your momentum is bringing you toward your intended target before you field the ball. A good example of this is shown in the highlight below, where Willi Castro sets himself up (7-8 second mark) to throw out one of the fastest players in baseball.

While Wallner’s top-end speed is fine (55th percentile), his five-foot running splits further support what may be the underlying reason why runners are willing to test his arm. Given his size, it takes him longer to get going, which inherently impacts his reaction and burst times. This has a chain effect on his overall approach to the ball, which then mitigates his ability to consistently take advantage of the 97 mile-per-hour velocity he averages on his throws. Whether this is an area of his game Wallner can improve remains to be seen, but it at least provides us with a theory as to why runners tend to be so aggressive, despite his arm.

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[Blyleven2011]

I always knew there was something not quite right with his defense , I was aware of his throws not being accurate , but wasn't aware of the route to take to make the good throw to nab the runner ...

He should get a little better and that little bit I can accept  , he won't be a kepler in right field  , Kepler was good , no question  ...

[NYCTK]

The defensive instincts of a DH. Not ideal! 

[nicksaviking]

I really think it has less to do with the defender than the situational offense.

I'm sure opposing teams make a cursory study of the defenders, but the 3B coach is going to send the runner based WAY more on the speed of the runner, the angle the ball is traveling, the number of outs, the inning, the score and who is on deck more than he's going to factor in who's in right field. 

How many such plays are we talking about, two, three dozen a season? We're working off of pretty small sample sizes.

[old nurse]

From fangraphs ARM (outfield arm runs): Outfielder’s get credit (plus or minus) depending on what the runners do on a hit or a fly ball out. A runner can stay put, advance, or get thrown out. A fielder will get credit not only if he throws out more than his share of runners, but also if he keeps more than his share of runners from advancing extra bases.

Wallner for his career is 1.0

[tony&rodney]

A couple of years ago (2023) Wallner was slow from picking up the ball or catching the ball to the actual throw. His transfers were a little slow. I didn't check that last year.

[tarheeltwinsfan]

Can Wallner pitch and bat or is it required to use a DH now?

[Riverbrian]

When I played. My decision making process in regards to taking the extra base, rarely was the strength of the arm the main consideration.  

It was the positioning of the fielder. If weak armed OF was near the ball or had the ball in his hands... I ain't going. If Strong armed OF wasn't near the ball or if he was heading the opposite way and had to turn his body to reset his position... I was going. 

Tagging on a fly ball. Yep... that's an arm decision unless it takes momentum to get to the ball.

The rest of the game (most of the game) it ain't arm... it's the OF'er getting to the ball... how quickly he gets there.

 

[JD-TWINS]

12 hours ago, NYCTK said:

The defensive instincts of a DH. Not ideal! 

Yep! He looks like a Legion Ball pitcher that plays OF a couple times a week to get his bat into the line-up. One thing the author did not mention is his slow, indecisiveness after fielding the ball. He’s not thinking ahead enough and he looks up and assesses where he wants to throw (many times not where he should throw) to show off his arm. Coaching, & more attention to detail, (coaching), should help improve him greatly. Principally playing RF I would think will help as well since it will become more “routine”.

[Linus]

Some of it is decision making.  If you judge that you can catch the ball then you want to take the most direct route.  If you can’t then you want to position yourself for making the throw.  Mixing up the two is a problem ala Jake Cave.  It’s easy to say that Buxton is a great fielder because he is fast (and he is).  His real genius is getting great jumps and knowing exactly where the ball is going and taking the proper route to the ball.  He rarely misses-judges whether he can catch the ball or not.  Wallner isn’t great at any of this.  While we all hope that RF will suit him better he has logged a lot of innings in the outfield in the minors so he kind of is what he is.

[Doctor Gast]

2 hours ago, JD-TWINS said:

Yep! He looks like a Legion Ball pitcher that plays OF a couple times a week to get his bat into the line-up. One thing the author did not mention is his slow, indecisiveness after fielding the ball. He’s not thinking ahead enough and he looks up and assesses where he wants to throw (many times not where he should throw) to show off his arm. Coaching, & more attention to detail, (coaching), should help improve him greatly. Principally playing RF I would think will help as well since it will become more “routine”.

I'm a fan of Wallner & I think he has the potential to be a good RFer. Instinct comes from plenty of playing time & coaching. He has had a lot of playing time but I question the coaching. I saw some improvement returning from AAA in the 2nd half. 

[rdehring]

Have been one of those who questioned Wallner's future because of his defense.  When he came up it was hard to watch.  Has he gotten better?  Yes, somewhat.  If he plays right field every day for the next few years he should continue to improve.

The problem is that he is what I describe as a big lumbering athlete.  They may be able to improve a lot of what he does, but you can't improve who he is.  That puts me in the group who wants to see his future as a DH who plays right field a couple days a week, or less.

[Blyleven2011]

40 minutes ago, Doctor Gast said:

I'm a fan of Wallner & I think he has the potential to be a good RFer. Instinct comes from plenty of playing time & coaching. He has had a lot of playing time but I question the coaching. I saw some improvement returning from AAA in the 2nd half. 

Wallner and Julien came up the same year ...

Julien showed a good bat but Terrible defense , but that defense improved  , then his bat failed and his defense floundered in his second year   ...

Wallner had a decent bat with strikeouts but his defense to start was uninspiring  but again he improved with more playing time at the position , he's considered better at right field because of his arm strength  , I'm not quite sure , he might end up being a better left fielder when someone better comes along to take rightfield away  ...

Wallner has power when he connects  , Julien needs to go to AAA and regain his focus on hitting and defense and earn his way back ...

[Karbo]

16 hours ago, Blyleven2011 said:

I always knew there was something not quite right with his defense , I was aware of his throws not being accurate , but wasn't aware of the route to take to make the good throw to nab the runner ...

He should get a little better and that little bit I can accept  , he won't be a kepler in right field  , Kepler was good , no question  ...

Let's hope his bat makes up for it. I would be interested to compare those with Larnach's.

[Steve Lein]

For me it's pretty simple: It looks like he's making a "bad" play a lot of the time, so this gives runner's confidence to try and stretch it.

His arm can more than make up for it when they do.

Honestly, baserunning of a lot of MLB players is a big pet peeve of mine. Not as many that should, understand momentum of fielder's related to throws they will have to make, or don't pay enough attention. 

Like, if you're tagging from second and the outfielder's momentum is taking him "away" from you or the base you want to go to, take that base! 

One of my favorite plays in all of baseball last year was this throw from Jurickson Profar against the Twins:
https://www.mlb.com/video/christian-vazquez-singles-on-a-line-drive-to-left-fielder-jurickson-profa

Profar had no business attempting this throw, to be quite honest, and Jeffers 100% made the right decision to go for it, based on Profar's momentum and what I'm talking about above.

But it was an all-time throw, and you just shake your head!

[Steve Lein]

4 hours ago, Riverbrian said:

When I played. My decision making process in regards to taking the extra base, rarely was the strength of the arm the main consideration.  

It was the positioning of the fielder. If weak armed OF was near the ball or had the ball in his hands... I ain't going. If Strong armed OF wasn't near the ball or if he was heading the opposite way and had to turn his body to reset his position... I was going. 

Tagging on a fly ball. Yep... that's an arm decision unless it takes momentum to get to the ball.

The rest of the game (most of the game) it ain't arm... it's the OF'er getting to the ball... how quickly he gets there.

 

Exactly! This is my pet peeve on baserunners not understanding this at the professional level!

[Riverbrian]

2 hours ago, Steve Lein said:

Exactly! This is my pet peeve on baserunners not understanding this at the professional level!

All my years of playing... All my years coaching... standing at 3B deciding weather to wave or stop sign runners. 

The decision is made based upon on where the fielder is in relation to the ball and what the fielder will have to do to get in position to throw.

The time it takes to stop, turn plant and throw is the difference between out and safe.

A weak armed outfielder can still throw the ball much faster than any human being can run.  

[Steve Lein]

20 hours ago, Riverbrian said:

All my years of playing... All my years coaching... standing at 3B deciding weather to wave or stop sign runners. 

The decision is made based upon on where the fielder is in relation to the ball and what the fielder will have to do to get in position to throw.

The time it takes to stop, turn plant and throw is the difference between out and safe.

A weak armed outfielder can still throw the ball much faster than any human being can run.  

I was also more cautious about a right-handed thrower playing RF, and left-handed thrower playing LF, on whether I'd try to stretch something down the lines into a double.

That's because they can "spin" to make that throw (and it can be a much stronger throw because of that) after fielding the ball, instead of having to stop their momentum entirely and reset before being able to make a throw. 

And this now reminds me of how I tore my ACL playing left field. I tried to stop that type of momentum to make a throw far too quickly 🤣 At least I made the catch!

[Riverbrian]

2 minutes ago, Steve Lein said:

I was also more cautious about a right-handed thrower playing RF, and left-handed thrower playing LF, on whether I'd try to stretch something down the lines into a double.

That's because they can "spin" to make that throw (and it can be a much stronger throw because of that) after fielding the ball, instead of having to stop their momentum entirely and reset before being able to make a throw. 

And this now reminds me of how I tore my ACL playing left field. I tried to stop that type of momentum to make a throw far too quickly 🤣 At least I made the catch!

And everybody watching that game... They Knew... Without a doubt... They knew... That you were going to make that catch. 

[Steve Lein]

3 minutes ago, Riverbrian said:

And everybody watching that game... They Knew... Without a doubt... They knew... That you were going to make that catch. 

Haha! It is actually kind of a fun story... None of the following is made up, I swear on my life about that!!! (I think this story is in my bio on here, as well)

Town Team game, Crow River Valley League. It was being broadcast on the local radio station, KGLB out of Glencoe, MN.

It was 9th inning and we were winning by 2 or 3, but they had the based loaded and we had just one out. A lefty that I knew liked to go the other way was up, so I was ready.

He of course did, and sent a looper down the line my way. It would have been a few feet fair if it landed, but I caught it at full sprint and glove fully extended out in front of me. This is the part where I should have done a slide, but instead I tried to stop on a dime and plant for a throw home with my right leg. I'll never forget the sound, or what it felt like having your leg bow out in a lateral direction that it's not supposed to... before I hopped one-footed on my left leg, and flung the ball toward the infield as best I could before crumpling to the ground.

Walked off under my own power, but I knew.

They got one run on that play, but we went on to win the game, likely because of me getting hurt. That was because the guy who took over left field for me was much younger and faster, and made a diving catch to snag a hard liner for the third out on the next hitter.

An added element of weirdness to this, was my older brother had torn his same ACL on the same field, almost exactly a year prior, doing the same thing playing in the outfield. But he was in right-field running down a ball in the gap. I came off the bench for him in that game.

[Riverbrian]

7 hours ago, Steve Lein said:

Haha! It is actually kind of a fun story... None of the following is made up, I swear on my life about that!!! (I think this story is in my bio on here, as well)

Town Team game, Crow River Valley League. It was being broadcast on the local radio station, KGLB out of Glencoe, MN.

It was 9th inning and we were winning by 2 or 3, but they had the based loaded and we had just one out. A lefty that I knew liked to go the other way was up, so I was ready.

He of course did, and sent a looper down the line my way. It would have been a few feet fair if it landed, but I caught it at full sprint and glove fully extended out in front of me. This is the part where I should have done a slide, but instead I tried to stop on a dime and plant for a throw home with my right leg. I'll never forget the sound, or what it felt like having your leg bow out in a lateral direction that it's not supposed to... before I hopped one-footed on my left leg, and flung the ball toward the infield as best I could before crumpling to the ground.

Walked off under my own power, but I knew.

They got one run on that play, but we went on to win the game, likely because of me getting hurt. That was because the guy who took over left field for me was much younger and faster, and made a diving catch to snag a hard liner for the third out on the next hitter.

An added element of weirdness to this, was my older brother had torn his same ACL on the same field, almost exactly a year prior, doing the same thing playing in the outfield. But he was in right-field running down a ball in the gap. I came off the bench for him in that game.

I tore my ACL or one of my CL's... The inside of the knee one... whatever CL that is. 

Mine happened at the office Christmas Party. 

Limbo Contest. I was probably in my 40's... It was down to me and a 22 year old girl... Everybody was watching... nobody could believe I was keeping up with her. I was under the damn bar and I felt it pop. 

It happened early in the night... I stayed past 1AM to close the place down... Limped around slightly but I can't say that I was in pain. 

Woke up the next morning. Got out of bed and fell into the closet. The knee was barking, my injury had arrived and it was clearly not working the first step out of bed.

Was on crutches for the next few weeks until I threw them away out of pure annoyance. Was given the option for surgery but at my age... the Doctor and I agreed... that surgeon would draw a fake moustache on me while I was under. So, I just let it get better over time and it healed up,

Just a tish of Arthritis in that spot from time to time, if I piss it off by standing too long or get too obsessed with the Twins platoon strategy. 

I want to be clear... I was under that bar... I would have won that limbo contest.

It become company policy that limbo contests were no longer allowed at Xmas parties. 

[gman]

Wallner has split his outfield time for the Twins pretty evenly between LF and RF. He only played right field in 33 games last year. I think you should the guy sum slack, if he is playing defense the same way in 3 years find another spot for him. But, right field was always the spot for the worst defender best hitter on a team. Next to first base. He would be a big target at first.

[RpR]

On 2/5/2025 at 10:37 AM, rdehring said:

Have been one of those who questioned Wallner's future because of his defense.  When he came up it was hard to watch.  Has he gotten better?  Yes, somewhat.  If he plays right field every day for the next few years he should continue to improve.

The problem is that he is what I describe as a big lumbering athlete.  They may be able to improve a lot of what he does, but you can't improve who he is.  That puts me in the group who wants to see his future as a DH who plays right field a couple days a week, or less.

Wishful thinking, which is the main reason a goodly number of newbies are on the team.

[RpR]

2 hours ago, gman said:

Wallner has split his outfield time for the Twins pretty evenly between LF and RF. He only played right field in 33 games last year. I think you should the guy sum slack, if he is playing defense the same way in 3 years find another spot for him. But, right field was always the spot for the worst defender best hitter on a team. Next to first base. He would be a big target at first.

3 years, good grief, the Twins are not a AAA team.