3 relievers with rebound potential the Pirates should sign this offseason

Caleb Thielbar

Caleb Thielbar had three straight seasons from 2021 through 2023 with an ERA under 3.50 while striking out over 30% of his opponents with a 30.6% K%. Thielbar also only walked batters 7.3% of the time, keeping control nicely. Unfortunately, his 2024 season did not look nearly as good on paper.

Thielbar pitched 47.1 innings, working to a 5.32 ERA, 4.10 FIP, and 1.56 WHIP in his age-37 season. The southpaw saw his K% plummet to 24.5%, while his walk rate rose to 11.1%. Thielbar's 1.14 HR/9 was about average for him, as he'd posted a 1.17 HR/9 throughout his three previous seasons. 

Despite Thielbar's advancing age, his stuff looked as good as ever. His 93.2 MPH four-seam velocity represented the highest average of his MLB career. Both his sweeper and curveball saw an uptick in velocity. Stuff+ pinned him at 111, which was the best of his career as well. His 105 Location+ indicated that he was executing his pitches.

Expected numbers were kinder to Thielbar's work. He had a sub-4.00 SIERA at 3.95, along with a 4.21 xFIP. His main issue was his batting average on balls in play. Over the previous three seasons, Thielbar averaged a 3.33 ERA with a standard .294 BABIP. This past season, Thielbar had a .331 BABIP.

Thielbar also posted an 87.1 MPH exit velo and 10% barrel rate the previous three seasons, compared to 88.2 MPH with a 10.1% barrel rate this year.

Despite approaching 40, Thielbar still has the stuff and some decent numbers under the hood. A low-cost deal to add a lefty to a bullpen that needs it badly could work out very well for the Pirates. Thielbar is another lefty with a lot of potential to rebound in 2025.