Oakland Athletics closer Trevor Rosenthal will undergo surgery for thoracic outlet syndrome, Jon Heyman of MLB Network reported.
Rosenthal, who signed a one-year, $11 million deal with Oakland in February, is expected to be out for 12 weeks. Heyman reported that Rosenthal had vascular compression so the surgery was needed.
Rosenthal posted a career-best 1.90 ERA last season. He recorded 11 saves, finishing the season with 38 strikeouts in 23 2/3 innings in 23 appearances with the Royals and the Padres.
Injuries are no stranger to Rosenthal, whose 2018 season with the Cardinals was ended by Tommy John surgery.