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Griffin Jax, relief weapon?

Perhaps lost in the highly-touted pitching prospect excitement, Captain Jax is sliding his way into Rocco’s circle of trust

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Detroit Tigers v Minnesota Twins Photo by David Berding/Getty Images

The Twins’ long-awaited pitching development pipeline has generated quite a bit of excitement during the team’s recent stretch of good play. Joe Ryan has been lights out to start the season, looking like a front-line starting pitching and quickly quieting concerns about his fastball reliance holding him back from being a viable starter. Bailey Ober has continued throwing quality innings, just like he did last season. Jhoan Duran has overwhelmed opponents and Pitching Ninja with his incredible power stuff out the bullpen and has quickly seized a high leverage relief role. Josh Winder, who, in just about any other recent era of Twins’ baseball would be a rookie sensation, has flown under the radar as a long-relief/spot starter swingman that just gets people out.

Finally, it looks like the homegrown arm plan is producing the kind of fruit the front office had promised.

Somewhat lost in all of that prospect hype is the development of right-hander Griffin Jax, who is quietly positioning himself as one of manager Rocco Baldelli’s most trusted relievers in his second major league season.

That burgeoning trust became evident Monday night. Nursing a 2-1 lead in the 7th inning against Baltimore, Baldelli turned to Jax to face the Orioles’ fifth, sixth, and seventh hitters. It was the type of spot that often belongs to more established veteran relievers. Jax calmly sent down the Orioles in order on 15 pitches via a harmless fly-out to center and two called strikeouts.

The situation Jax entered was a borderline “high-leverage” spot. Fangraphs measured the leverage index at 1.91 when he entered the game, which is technically a “medium-leverage” situation (2.0 is the cut-off for “high”). Nonetheless, it was easily the highest pressure situation Jax has faced in his short big-league career. Prior to Monday, Jax (who has started 14 of his 24 career appearances) had never before entered a game where the leverage index was even greater than 1.0.

That Baldelli turned in that spot to a young pitcher who had a 5.93 career ERA (6.17 FIP) prior to that appearance, might qualify as a surprise. He had more veteran options available. He could have turned to long-established late and close reliever Tyler Duffey for the second day in a row. Cody Stashak and Caleb Thielbar threw last on Saturday and were presumably available. Veteran Emilio Pagán had not pitched in almost a week after taking on save opportunities in his previous few outings.

But, Baldelli went to Jax. And he delivered.

Our possible surprise at that move is probably rooted in our understanding of the pitcher Jax had been, not the pitcher he has become. Upon moving to the bullpen full-time this season, Jax has made a major adjustment to his pitch mix. That adjustment is entirely predictable for those following the Twins the last several seasons. Like Ryne Harper, Ryan Pressly, Duffey, Stashak, and Matt Wisler before, Jax moved to the pen and began heavily featuring his breaking pitches, as you can see with the blue line on the right-hand side of the chart below:

Data from Statcast

Last season, as predominantly a starting pitcher, 40.1% of the pitches Jax threw were sliders (31.1%) and curveballs (9.0%). This season, in six appearances working only out of the bullpen, 66.3% of his pitches have been breaking balls (51.5% sliders, 14.8% curveballs). As a result, Jax has more than halved his fastball usage from 45.9% down to 21.9%. He’s had two appearances where he did not even throw a single fastball. He’s done that despite averaging 94.0 miles per hour with his heat, an increase of about 1.6 miles per hour over last season.

It has been the en vogue trend across baseball the past several years for pitchers to identify their best pitches and then lean on them heavily, especially for relievers in short bursts. For pitchers who can spin effective breaking pitches that has meant doing so repeatedly, at maximum effort, conventional wisdom about pitching backward and the importance of establishing the fastball be damned.

The results of that approach speak for themselves and the preponderance of wicked breakers is one of the major factors in why the overall baseball offensive environment is, by some measures, at its lowest point since the 1960s.

Jax is the latest Twin to reap the benefits of this approach. While Jax’s slider yielded a +7 cumulative Statcast run value and +1.7 runs per 100 pitches last season (positive run values are bad for pitchers), the underlying data showed the pitch had more potential. Opponent’s hit .226 against the pitch, with an expected batting average of just .189, and a 36% whiff rate. The challenge was when hitters did make contact, it was often loud and damaging, as evidenced by a .470 slugging percentage and 7 home runs hit against Jax sliders in 2021.

So it had potential as a swing and miss weapon last season but needed some adjustment. This season, not only is Jax throwing the slider as his primary offering, but he’s also throwing it significantly harder than he did previously – something that is logically easier to do in shorter appearances:

Data from Statcast

Jax has also increased the average velocity of his curveball from 79.8 mph last season to 82.4 mph this year. Naturally, the increased velocity has changed the movement profile of the pitches. Both are dropping about five inches less according to Statcast (which measures with effects of gravity included) but still have roughly league average vertical movement relative to their velocities.

But it’s horizontal movement, especially relative to velocity, where Jax becomes unique. With the increased velocity on his breaking pitches, he’s given up about an inch of side to side break on his slider and about two and a half inches on his curveball. That said, Jax’s 10.1 inches of horizontal break on his slider is almost five inches more than what other 86-mile-per-hour major league sliders get. That works out to about 87% more than average at that velocity and places Jax in the top 25 pitchers in baseball for slider horizontal break relative to velocity according to Statcast’s Pitch Movement Leaderboard. There are 86 pitchers shown on the leaderboard this season that have greater raw horizontal movement on their sliders, however, every single one of them throws their slider at a lower average velocity than Jax.

Jax explained to FanGraphs’ David Laurila earlier this season that the development of his slider is the result of some low-risk experimentation during the pandemic and a unique, homegrown grip (picture included in the link):

“I was facing Trevor Larnach, Alex Kirilloff, Nick Gordon — some of our younger guys — every time I was on the mound. I was throwing fastball/changeup/curveball, like I’ve done my entire life. Maybe the seventh time they faced me, I wanted to show something different. I was toying around in catch-play, right before I was about to go on the mound, and was like, ‘What if I just turned my curveball a little bit?’ That’s how I got the slider I have now.

“The coaches were like, ‘What did you just throw?’ I said that I was just kind of messing around and that I was supposed to be throwing a slider. They said, ‘Yeah, throw that again.’ We just continued working on it, working on it, and got to the point where I can throw it comfortably and confidently. Now it’s my lean-on, pretty much every time I’m out there.”

Conversely, his now-hard curveball gets far less horizontal break (-62%) than average curveballs at that speed, making it a vertical breaking weapon to pair with the sweeping slider and his riding four-seam fastball that also features above-average vertical and horizontal movement.

Jax has the ability to attack hitters north-and-south and east-and-west, as he went on to explain to FanGraphs:

“When we look at pitchers nowadays, you kind of put them in two categories. You put them in either as a north-south guy — like a carry guy — or you put them in as an east-west sinker guy. My fastball/curveball profile is in the north-south — fastball at the top of the zone, curveball at the bottom — and my slider is pretty much pure east-west. When you’re showing a scouting report on a pitcher… for me, they’re looking primarily top-of-the-zone, bottom-of-the-zone. But when I’m able to throw my slider to the side, off the plate to righties and in to lefties, it’s a completely different movement than what they’re expecting. My slider is more sweepy. It has very little depth. It’s almost all horizontal.”

Jax demonstrated that north-south-east-west combination to great effect against Detroit’s Derek Hill late last week, as you can see in the video.

The high-velocity sweeping slider gives Jax a swing-and-miss weapon that he was lacking as a starting pitcher. The early returns on Jax out of the bullpen are highly encouraging. His Statcast summary profile is a sea of good indicators and he currently ranks in the 88th percentile among all pitchers in both whiff rate and chase rate.

Now, opposing hitters have swung and missed at 50% of Jax’s sliders and have produced just two singles in 18 at-bats that have ended on the pitch so far in 2022. On a per pitch run value basis, Jax’s slider has been worth -1.8 runs per 100 pitches so far this season, placing him in the top 30% across the league and in the same general area as noted breaking ball experts Shane McClanahan, Carlos Rodón, and Noah Syndergaard (and Joe Ryan!).

While he uses his curveball more sparingly, its whiff rate has also nearly doubled from 7.9% to 15.4% and opponents have just one single in eight at-bats that have ended with a hook this season.

Time will tell how the league adjusts to his new breaking ball-heavy approach. He’s thrown all of ten innings and just ~40% of his pitches (~33% of his breaking balls) in the strike zone this season (compared to ~50% and ~40% last season, respectively), so it is likely that he will need to prove that he can consistently throw quality strikes with this approach once the league starts to lay off more of those sliders and curveballs out of the strike zone. But, these adjustments clearly make him a viable option for important bullpen work and the Twins manager seems to be growing more and more comfortable giving him meaningful chances.


John is a writer for Twinkie Town and Pitcher List with an emphasis on analysis. He is a lifelong Twins fan and former college pitcher. You can follow him on Twitter @JohnFoley_21.