Trust the Stuff: Griffin Jax's Peripherals Suggest He Could Be a Top Gun in the Bullpen

From becoming the first player out of Air Force Academy in MLB history, to debuting as a mid-level starting pitcher prospect in 2021, to locking down high-leverage situations out of the Twins’ bullpen, Griffin Jax has gone through more turns than an F-22 Raptor aircraft. Now, manager Rocco Baldelli has entrusted him to be a late-inning, shutdown relief weapon. 

If you were to only look at his ERA as the true indicator of his value, you’d be somewhat underwhelmed by his results this year. But if you look at nearly any other figure in his stat line, it’s clear that Jax has the stuff to be a Top Gun in the Twins’ bullpen for the foreseeable future. 

Let’s be perfectly clear, nobody should be making any declarations about a 28-year-old pitcher based on a good-not-great ERA after the first month of a season. His 3.86 ERA would be totally welcome, if not celebrated by virtually every ball club. But some Twins fans aren’t quite as sold on Jax, and a lot of that probably stems from the three lone blemishes on his game log. 

He’s only given up earned runs in four of his 15 appearances, but the modest level of competition in that quad of games seemed to magnify their relevance. He coughed up two earned runs to the Miami Marlins in the first week of the season, gave up two runs to the Washington Nationals on April 21st, was responsible for the game-tying run in the lone loss to the Kansas City Royals last Saturday, and gave up the go-ahead run in Wednesday's loss to the Chicago White Sox. Those are four teams that are now projected to be well-below average when all is said and done in 2023, which unjustly caused many raised eyebrows when Jax didn’t mow them down. 

But even the best relievers give up runs every now and then, sometimes due to just having an off-day and sometimes it’s just bad luck. For Jax this year, the argument can be made that it’s mostly been the latter. His strikeouts are as high as they’ve ever been (10.4 K/9), his walk rate is the lowest of his career (5.7%) and he is among the best in the league when it comes to inducing soft contact. Just look at all of the stellar marks in his Baseball Savant profile. 

Not only are his batted-ball numbers quite strong, even elite in some regards, but they suggest that the hits he’s given up in his hiccup games are softer than they came across in the box score. Perhaps his performance is better represented by his Fielding Independent Pitching, which is worlds better than his ERA (1.75 FIP). His .257 Batting Average of Balls In Play (BABIP) is dead-on when compared to his career rate, and his opponents’ lack of ability to land a hit off of him is laughable (.180 batting average against).

So when teams like the Nationals or the Royals score off of him in highly-improbable ways, it’s hard to knock the guy. Maybe it’s bad luck, maybe Jax broke the unwritten law that a righty reliever should never throw two changeups in a row to a right-handed hitter, or maybe we’re talking about a comically small sample size. Either way, Jax doesn’t deserve much haste when looking at his season to this point. If he can keep playing to his strengths, his modest surface numbers will catch up to his peripherals.

Notably, his strengths are plentiful. Jax has been lethal against left-handed hitters (.083 on-base percentage, best in MLB according to Inside Edge), opponents have a 38% chase rate against him (15th-best in MLB) and he’s allowed just a .105 slugging percentage on his slider (7th-best). 

So there’s plenty to like with the former Air Force Academy Falcon, and the light turbulence that fans have experienced is worth it in the grand scheme of things. If he stays on the flight plan that he’s currently using, projections suggest Jax could be as successful as a Tom Cruise blockbuster. 

What do you think? Is Jax bound for a breakout? What do you think he needs to do to be the Top Gun in the Twins’ bullpen? Let us know your thoughts in the comment section below.