The Oakland Athletics made a relatively pricey expenditure in February when they signed reliever Trevor Rosenthal to a one-year deal worth $11 million. The A's envisioned Rosenthal replacing the departed Liam Hendriks as their closer. Alas, that hasn't come to fruition. The A's announced Thursday afternoon that Rosenthal has undergone surgery to address thoracic outlet syndrome.
Rosenthal will be re-evaluated in eight weeks. A traditional recovery period is around 12 weeks, which would put Rosenthal back sometime in mid-to-late July.
In the meantime, the A's are left scrambling to replace production from last year's ace closer, Liam Hendriks. Manager Bob Melvin mentioned right-hander Lou Trivino has a strong possibility (via Shayna Rubin) before Thursday's game against Houston. Trivino has only allowed one run on one hit in 5 2/3 innings with six strikeouts and two walks so far this season. Other late-inning options are lefty Jake Diekman and righty Sergio Romo.
The A's started the season 0-6, but managed to take Wednesday's game against the Dodgers.
As for Rosenthal, it could be a long road back. Although thoracic outlet syndrome surgery doesn't have the name brand recognition that Tommy John surgery does, it's arguably more threatening to a pitcher's career. As Jay Jaffe of FanGraphs concluded in June 2020: "the range of outcomes is quite wide when it comes to pitchers who have undergone surgery to correct TOS, and there aren't a ton of success stories." There are, however, a number of tales of pitchers who haven't recovered from the surgery, including most famously Matt Harvey.
Rosenthal essentially saved his career last season, making 23 appearances split between the Kansas City Royals and San Diego Padres and compiling a 1.90 ERA and a 4.75 strikeout-to-walk ratio. The previous season had seen Rosenthal falter, largely with the Washington Nationals, as he walked 26 batters and allowed 24 runs in 15 innings.