5 Years After a 5-Year Break, Caleb Thielbar is the Cubs' Unsung Hero in the Bullpen

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The Chicago Cubs bullpen is ranked 12th in ERA (3.87) this season through August 4, although six relievers have an ERA under 3.00. That success is led by closer Daniel Palencia's 1.55 ERA, but Brad Keller (2.76), Drew Pomeranz (2.05), Ryan Brasier (2.95), and Taylor Rogers (2.38), who was acquired at the trade deadline, are all major contributors to the bullpen's success and are names people outside of the North Side of Chicago would recognize.

However, there's one reliever producing at a remarkable rate that is seldom talked about. Caleb Thielbar is having the best season of his nine-year career, save for his abbreviated campaigns in 2013 (rookie year) and 2020 (pandemic-shortened season). The lefty has thrown 42 innings thus far in 2025, which is the second most in the bullpen, and posted a 2.36 ERA, 39:12 strikeout:walk ratio, while holding hitters to a .166 batting average.

Part of what makes his season so special is the fact that he is 38 years old. He spent his last eight seasons with the Minnesota Twins; however, Thielbar left the game in 2016 and went on to be the pitching coach at Division II Augustana University in Sioux Falls, South Dakota. He wasn't known for a four-seam fastball that topped out at 90 mph, but rather his off-speed pitches that made people chase.

Thielbar returned to baseball in 2018, pitching in the Detroit Tigers' minor league system, and 2019, the lefty earned a spot on the Team USA baseball team. Pitching against college teams provided him with valuable experience in his primary role as a coach. He picked up tips by watching the top college teams in the country. Although Thielbar struggled in the Premier 12 tournament with a 16.20 ERA in 1 2/3 innings, at this time, his fastball was topping out at 93 mph and was catching the eye of MLB scouts.

The Twins then signed him again, and his career took off for a second time. In 2020, he made his MLB return and threw his first pitch in 1,923 days. Thielbar finished that season throwing a 2.25 ERA, with a 22:9 strikeout:walk ratio, and a .192 opposing batting average. The next three seasons, he finished with mid-3.00 ERAs, though in 2024, he had a 5.32 ERA, resulting in his not being re-signed by the Twins during the offseason.

The Cubs then took a chance on the 38-year-old, signing him to a one-year, $2.75 million contract. That's quite the discount for the production Thielbar has produced this season. Baseball Savant has harshly ranked the lefty in the 24th percentile for fastball velocity at 92.6 mph, but has him in the 98th percentile in expected earned runs (2.39), and in the 95th percentile in expected batting average (.199).

The Cubs' bullpen is loaded with elite arms that look to be a force in the second half of the season. Thielbar is an unlikely source for such production, but he has been one of the biggest success stories this season. Considering that we're coming up on the five-year anniversary of his five-year hiatus, he deserves a lot more love for the production he's brought to Chicago this season.