TAMPA — Yankees reliever Joba Chamberlain has started throwing off a half-mound as part of a rehabilitation program after elbow ligament replacement surgery.

Chamberlain threw at the Yankees minor league complex in Florida on Friday. The right-hander said the session on the 5-inch mound, which pitching coach Larry Rothschild and team vice president Billy Connors watched, went well.

Chamberlain went 2-0 with a 2.83 ERA in 27 relief appearances last season before surgery on June 16. He is expected to rejoin the Yankees at some point this 2012 season.