SCOTTSDALE, Ariz. -- San Francisco Giants right-hander Tristan Beck is scheduled to have surgery Monday to remove an aneurysm in the upper part of his pitching arm.

He will have the procedure at Stanford, where he was examined by a vascular specialist this week, and the timetable for his return to the mound is unclear until after the surgery -- but his availability for opening day is in doubt.

Beck was competing for a spot in the back end of the rotation for San Francisco, which has been out of the playoffs the past two seasons and hired new manager Bob Melvin to replace Gabe Kapler.

Beck, 27, went 3-3 with a 3.92 ERA over 33 appearances with three starts as a rookie last season.