Cardinals left-hander Zack Thompson suffered a tear in his left lat muscle, president of baseball operations John Mozeliak told reporters (including Derrick Goold of the St. Louis Post-Dispatch) today. Thompson will be shut down and then re-evaluated in three or four weeks, so Thompson will surely start the season on the Cards’ injured list.
It’s a tough setback for Thompson, who was competing for a job in the St. Louis bullpen and is still trying to find a niche for himself at the big league level. The 19th overall pick of the 2019 draft has amassed 118 career MLB innings over the last three seasons, topping out at 66 1/3 innings in 2023 while working first as a reliever and then as a starter over the season’s last six weeks.
Thompson had a 2.08 ERA in 34 2/3 frames in 2022, but then a 4.48 ERA from that larger workload in 2023. His peripheral numbers were still interesting enough to suggest that Thompson might take another step forward last season, yet the opposite happened — the southpaw was rocked for a 9.53 ERA over 17 innings as a starter and reliever, and didn’t return to the majors after being optioned to Triple-A Memphis in late April. Things didn’t exactly stabilize in the minors, as Thompson had a 4.40 ERA and 14.2% walk rate over 90 innings in Memphis, starting 20 of his 21 games.
While these struggles didn’t remove Thompson from the Cardinals’ future plans, there wasn’t any space for him in a rotation that is still full of veteran arms, plus other youngsters have now seemingly passed Thompson on the depth chart if a rotation spot did open up. Working as a long reliever or possibly a swingman would have allowed Thompson to build up more experience and confidence in the Show, unless St. Louis preferred to let him get on track as a starter in Memphis.
The league granted the Cardinals a fourth minor league option on Thompson during the offseason, giving the team the ability to send him back and forth between Triple-A and the majors during the 2025 campaign. It is quite possible Thompson would have started the season in Triple-A anyway, though today’s injury news will delay the lefty entirely until he is able to get back onto a mound. Thompson will then need to rebuild his arm strength, so it seems likely he’ll be sidelined until at least late April given the time he is set to miss in his shutdown period.