Reframing Dominant Twins Reliever Griffin Jax's 2025 Performance

[Chris Hove]

Image courtesy of © William Purnell-Imagn Images

Griffin Jax has had an up-and-down season, numbers-wise. He has a six-pitch arsenal, but he has primarily used three pitches this year. Jax also has excellent command of the fastball and good enough velocity, topping out around 97 MPH. His sweeper is his most frequently used pitch, but his changeup has missed more bats and been more efficient. He also features a sinker, cutter, and curveball, but he's thrown them only 13% of the time, combined. Jax has changed the way he approaches hitters in 2025, utilizing the sweeper and changeup as primary put-away pitches. His changeup is holding hitters at a .138 BA with a very low average exit velocity of 81.5.

Last year, his fastball was his second-most-used pitch, but this year, his changeup has increased from 16.7% usage to 25.4% usage. Of his 41 strikeouts, 38 have come either on the sweeper or the changeup. There's no doubt Jax has supreme confidence in throwing both pitches in two-strike counts.

Jax possesses great control and often hits his spots with his sweeper. No reliever in the game can match his punchout total for the year. The way he gets ahead of hitters sets him up to throw his changeup down in the zone or mix in his sweeper. Jax hasn't changed the way he throws the changeup. His velocity on it is around 92 MPH, which is a lot higher than most pitchers' changeups, but he also still creates a 14.4-inch gap in vertical movement between the fastball and the change, so there's no loss of depth based on the firmness of it. He gives hitters something more to think about with two strikes. 

If anything, his stuff looks as good as last year, and the shift in usage has unlocked more swing-and-miss for him, So why is he being hit harder, at least at a first read of his surface-level numbers? That's the question we want to answer here.

His fastball velocity hasn't changed much, averaging around 97 MPH. One factor is the lack of movement he has on his fastball, which appears to be fairly straight. While the velocity is good, if Jax primarily throws it in the zone, hitters see it easier and track it much better than they might see other heaters. According to Alex Chamberlain's Pitch Leaderboard, his fastball only averages one inch of vertical movement and 0.7 inches of horizontal movement, relative to a true dead zone heater based on his arm angle. According to Statcast, his fastball Run Value is among the lowest in the league at -4; hitters are turning in a .350 batting average and an .850 slugging average against it. Additionally, their average exit velocity is a staggering 98.8 MPH, compared to 93.2 MPH last year. 

It's counterintuitive that hitters make such solid, sometimes lethal damage on Jax, given how nasty his stuff is. Basically, though, it seems that batters are getting the head of the bat out and working uphill when they get to the contact point against him. Hitters know they have to guess when facing Jax. Most of them guess wrong, but when they guess right (especially on the fastball), it can be an easier pitch to catch flush than other pitchers'. Please take a look at these charts, which show the attack direction (horizontal angle of barrel movement) and attack angle (vertical angle of the same thing) on all competitive swings against Jax since the middle of 2023, when they made bat-tracking data public.

The average swing against him has an attack direction of 0° and an attack angle of 9°, a combination that tends to result in high exit velocities and balls in the air (albeit to the big part of the park, where relatively few of those well-struck air balls go for homers). He induces plenty of whiffs, but when hitters do make contact against him, it can cluster in the area where that contact tends to get loud. For context, compare Jax's distribution of swing timing elements with those against Jhoan Duran:

The average attack direction against Duran is 7° toward the opposite field, and the average attack angle is 4°. You'd rather have Jax out there if you need to miss a bat, but Duran's array of swings induced is more likely to ensure weak contact when batters do find the ball.

Now, Jax's results have matched his process much better this month. He's only yielded two earned runs in May. His ERA is 1.42, and his WHIP is 0.79. Jax will always have a good strikeout-to-walk ratio, which is 20:2 this month. Mixing in his changeup more and using it more as an out pitch will still make him a pitcher whom batters don't want to see in the late innings. If he can spot the sweeper like he has been this year, then we can hope he sneaks that fastball in on hitters and gets a few more whiffs.

He has thrown six consecutive scoreless innings, with a 13:1 strikeout ratio while only allowing two hits. The Twins will lean heavily on Jax in the late innings and almost in any scenario, but with Duran also backing him up, the Twins still feature one of the best 1-2 punches in the back of the bullpen. It's just a bit more boom-or-bust with Jax.

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[Blyleven2011]

Jax seems to have his MOJO back , if he can get more outs by sweeper or change up , then by all means keep doing so  ...

I have no worries about Jax  , his wrinkle to start the season was abnormal compared to last year , but he's got the smarts to right the ship if it occurs again  ...

No worries ...

[Chris Hove]

12 minutes ago, Blyleven2011 said:

Jax seems to have his MOJO back , if he can get more outs by sweeper or change up , then by all means keep doing so  ...

I have no worries about Jax  , his wrinkle to start the season was abnormal compared to last year , but he's got the smarts to right the ship if it occurs again  ...

No worries ...

No worries about the fastball? Should he just keep a two pitch out mix? Im generally interested on how he goes along from here.

[Blyleven2011]

23 minutes ago, Chris Hove said:

No worries about the fastball? Should he just keep a two pitch out mix? Im generally interested on how he goes along from here.

I was going to write about his fastball but I guess I didn't think it was necessary because he's using it less and his primary pitches are his sweeper and change up , but sneaking a fast ball in won't hurt either , just keep it a high strike ...

[arby58]

2 hours ago, Chris Hove said:

No worries about the fastball? Should he just keep a two pitch out mix? Im generally interested on how he goes along from here.

I suspect it is how he uses the fastball - he won't become a two pitch pitcher. Everybody needs to be able to establish a fastball, but you don't have to use it in certain counts or situations.

[Doctor Wu]

Very good overview of Jax and his season so far. After those scary early weeks it seems like he is back in a groove again . I still have a hard time getting my head around all the various pitch mixes that these guys have in their arsenal, so articles like this are very helpful to me. 

[JD-TWINS]

Jax, 7 or 8 days ago was tied for most “holds” in baseball.

His strikeout rate is 15K’s/9 innings.

In his last 5 outings he’s thrown 5 innings - giving up 2 hits - zero walks - no runs - with 11 strikeouts. 

The guy is more than “past his early struggles”, he’s dominant!

Opposing hitters have nearly no chance against the sweeper - his change-up moves too much to hit and they have to time it up. Thus, they all go up and sit fastball because that’s there only chance. If he’s dotting the outside corner or if it’s elevated, it too is nearly untouchable. He seems to have regained his command and is electric on the mound!

[Linus]

Nice article - informative.