The Minnesota Twins’ bullpens have fluctuated since Derek Falvey took over the front office. The team slowly built a solid bullpen in 2019, and a strong second-half surge gave the unit a 4.17 bullpen ERA that was top-10 in baseball. It was even better in 2020 when the Twins were sixth in baseball with a 3.62 bullpen ERA. But before that, a 4.39 bullpen ERA in 2021 (21st in MLB) and a 3.84 ERA in 2022 (15th) were part of why they had disappointing seasons those years.
Minnesota’s bullpen didn’t improve overnight last year. The unit ended the season with a 3.95 bullpen ERA, which ranked 15th in baseball. Toward the end of the season, the Twins relied on the top half of their bullpen to become more productive, with a 3.76 ERA. With his 2.15 career ERA and 33.1 percent strikeout clip, Jhoan Duran continues to be the centerpiece of not just the Twins bullpen but one of the most effective closers in baseball.
The Twins need to complement Duran more to create an impactful bullpen. They often used Caleb Thielbar and Brock Stewart in late-inning roles. Stewart and Thielbar are impactful pitchers, but neither has Griffin Jax’s ceiling.
Since the Twins converted Jax from a starter to a reliever in 2022, he has a 3.60 ERA in 137.2 innings pitched, with a 25.9 percent strikeout rate. It’s been a good run for Jax, but it feels like he hasn’t reached the ceiling of how productive he can be. Jax has the ceiling to become Minnesota’s most reliable high-leverage reliever outside Duran. Next season will give him a clear path to establish himself as that kind of arm.
Moving from the rotation to the bullpen allowed Jax to maximize his velocity. His fastball had an average speed of 92.6 mph in 2021, but he topped out at 96.5 mph as a reliever in 2023. Becoming a reliever also meant Jax could tighten up his pitch repertoire. He still has five pitches but mostly uses his sweeper (52.8 percent) and 4-seamer (22.4 percent). The former is far and away his best pitch. Jax creates a 7-run value when throwing a sweeper.
Jax’s ability to generate spin better as a reliever played a big role in his success. Combine his 84th-percentile and 80th-percentile fastball velocity and spin rates, and you get a career-low 3.3 barrel rate in 2023.
Jax’s absolute filth on his pitch breaks earned him high praise from PitchingNinja.
The Twins have had some high-end talent in their bullpen recently. That was especially true during the playoffs last year. Minnesota put starters Kenta Maeda, Louie Varland, and Chris Paddack in the bullpen. Throw that in with Stewart returning from injury, and it infused the reliever corps with high-end talent.
The Twins re-invested in the bullpen over the winter, adding Justin Topa, Steven Okert, Jay Jackson, Josh Staumont, and Zack Weiss. Many outlets project Minnesota’s bullpen as one of the best in baseball for 2024. During the regular season last year, the Twins’ relief corps wasn’t deep enough to take pressure off the high-leverage arms.
Jax has earned Baldelli’s trust to become a high-leverage arm in 2023. Part of the fanbase is still uneasy about crowning Jax as a surefire high-leverage arm because of how last season started. In Jax’s first 25 appearances last year, he had a 4.63 ERA in 23.1 innings and a -0.62 win probability added. But during that span, his 8.6 percent walk rate wasn’t extraordinarily high, and an 87.5 mph average exit velocity was still below league average (88.4 mph).
Last season, Jax was getting BABIP’d (batting average on balls in play) to death. Opposing batters hit too many balls with weak contact that found the outfield grass and mounted against Jax. His 2.15 FIP and a .347 BABIP over the first stretch of the season resulted from bad luck rather than bad pitching.
But his BABIP luck changed during the rest of the season, and Jax looked like the reliever he was capable of being. His ability to pitch in high-leverage situations jumped up to a 0.43 WPA in 42 innings over 46 appearances with a .259 BABIP. During that same span, Jax had an 86.3 mph average exit velocity.
However, he still has work to do to become the clear second option on Minnesota’s bullpen depth chart. Getting rid of bad luck sounds simple, but it’s not easy. First, he must eliminate baserunners because an elite arm doesn’t have a 1.18 WHIP. An increase in strikeouts can obviously help with the BABIP lousy luck. A 26.9 percent strikeout rate for Jax in 2022 was just a 24.8 percent clip in 2023. Getting ahead early in counts would be an excellent way to do that, considering he had a 56 percent first-pitch strike rate. That was a career-low and far below the 60.9 percent league average number.
Jax is off to a great start in spring training. He’s held opposing lineups scoreless through five innings while racking up 10 strikeouts. As long as Jax handles stretches of bad luck well, there’s no reason to think he can’t sit just below Duran in Minnesota’s bullpen hierarchy.
Jax has worked himself from an afterthought as a starting pitcher to one of Minnesota’s nastiest bullpen pitchers. He’s put together quality back-to-back seasons, earning increasingly more high-leverage innings. Some tweaks and a change in fortune are all standing in his way to becoming one of the best setup men in baseball.
