Oakland Athletics right-handed reliever Trevor Rosenthal underwent surgery on Thursday after he was diagnosed with severe neurovascular compression.
The procedure, involving the removal of Rosenhal's first rib, a pec minor release and scalene release, was performed by Dr. Gregory Pearl in Dallas, Texas.
Rosenthal will remain in Dallas until Sunday and return to see Dr. Pearl for a checkup in approximately eight weeks, the team said.
The A's transferred him to the 60-day injured list.
The A's signed Rosenthal to a one-year, $11 million contract in February with the hopes he could replace closer Liam Hendriks who signed with the Chicago White Sox as a free agent.
Rosenthal, 30, has 132 saves and a 3.36 ERA over eight major league seasons.