Confidence in the Minnesota Twins’ front office took a monumental blow this season after they failed to build a serviceable bullpen and turned a back-to-back division champion into a last-place team. Derek Falvey and Thad Levine were brought in because of their previous work developing pitchers throughout the farm systems in their previous jobs, yet the Twins’ pitching has been a disaster this year.
Not only has their pitching staff regressed, but the bullpen, the team’s strength over the last two seasons, has fallen to one of the worst in baseball, ranking 26th with a 4.76 ERA from the relievers. Every pitcher the Twins brought in to bolster the bullpen has struggled. Hansel Robles had a 4.91 ERA in 44 innings before being traded to the Boston Red Sox. Alexander Colomé bounced back nicely after a rough first month, but it was already too late for the Twins to compete for the postseason by the time he turned things around.
Shaun Anderson, Glenn Sparkman, and Luke Farrell were also brought in as fliers to create organizational depth in the bullpen. The Twins took a lot of swings and missed at nearly every opportunity when it came to reloading their once-impressive rotation.
But one of Minnesota’s most impactful relievers this season has been a guy flying under the radar the entire time: Caleb Thielbar.
Thielbar’s path to the majors is more than a nice story. The Northfield, Minn. native by way of Augustana in Sioux Falls, S.D. worked all the way up to sign with his hometown team in 2013 after spending time with the then-Independent League St. Paul Saints. But Thielbar pitched for some bad Twins teams that lacked the ability to develop its hurlers. After posting a 1.76 ERA over 46 innings in 2013, Thielbar recorded a 3.40 ERA in 47.1 innings in 2014 and only logged five innings the next season before his big league career was put on hiatus.
Thielbar would continue going back and forth between the minor leagues and the Saints, spending time in the farm systems of the San Diego Padres, Miami Marlins, Detroit Tigers, and Atlanta Braves. Still, he never reached the majors with any of those teams. That was until Falvey and Levine took their shot on the lefty reliever by signing him to a minor league deal after the 2019 season.
Falvine had just built a solid bullpen in Minnesota, so the incentive was there to add Thielbar on a low-risk deal to see what pitching coach Wes Johnson could do with an extra lefty reliever. The return on their investment for the now-journeyman reliever was as big as they could have hoped for. Last year he had a 2.25 ERA in 20 innings with a 9.90 K/9 rate, the best in his career.
The feel-good story was back, but it was uncertain if he could sustain that success over a full 162-game season.
As the 2021 season nears its final month, Thielbar’s success has continued with a 3.66 ERA, a 3.17 FIP, a .218 opponent batting average, and a 1.14 WHIP in 46.2 innings this season. His strikeouts have also improved to a career-high 11.19 K/9 rate. After Taylor Rogers, Thielbar’s 0.7 WAR ranks second-highest out of all Twins relievers this season.
The Twins were able to showcase their ability to develop pitching through hidden gems like Thielbar because they could modernize his approach in a few different ways.
One change the Twins made in Thielbar’s approach has been his pitch selection: They lowered his fastball and had him rely more on his slider. He relied mainly on his fastball during his first stint in Minnesota, throwing it around 64% of the time from 2013-15. Thielbar also throws a curveball as part of his secondary pitches after dropping the change-up in his second stint. Below are his pitch usages over his Twins career, according to FanGraphs.
In addition to the change in usage, Thielbar has also increased the velocity on his fastball, slider, and curveball. Another modern adaptation to Thielbar’s approach was his spin rate. The spin-rate statistic has only been around since 2015, and that season he only threw five innings. Given the Twins’ pitching approach at the time, it’s likely his numbers weren’t much different from that season. Listed below are his spin rates, according to Baseball Savant.
Thielbar has increased his performance and earned manager Rocco Baldelli’s trust, going from just an inning-eating reliever to one the team can reliably use in high-leverage situations. His leverage index increased from 0.69 in 2013 to 0.96 in 2020 and 0.91 so far this season. The high-leverage use of the lefty has been crucial lately, with the Twins’ other big left-handed arm, Taylor Rogers, on the injured list. According to FanGraphs, with the increase in those situations, Thielbar has been able to earn a 1.28 clutch rating.
Thielbar started out as just a feel-good story when he was with the Twins in the early 2010s, and it seemed to be the case again when he found himself back on the bullpen again last year. But while other Twins relievers have faltered, Thielbar has risen to become one of their best bullpen arms. His continued success not only shows that he can be a future contributor to the team, but it’s also an example of Falvine’s ability to develop pitching, even in a down year for Minnesota’s bullpen.