The 2010 AL MVP was injured during Tuesday night's game against Seattle during a headfirst slide into first base in the seventh inning. He remained in the game but struggled with throwing balls and gripping his bat. Ian Stewart pinch hit for Hamilton in the ninth and struck out with the potential tying run on base in a 5-3 loss.
Los Angeles said an MRI Wednesday revealed a complete tear of the thumb's ulnar collateral ligament. After initially saying hand and wrist specialist Dr. Steven Shin would operate at Kerlan-Jobe Orthopedics in Los Angeles, the Angels said Hamilton will be examined by Shin on Friday to determine whether surgery is needed.
Hamilton was placed on the 15-day disabled list, and outfielder J.B. Shuck was recalled from Triple-A Salt Lake.
Speaking after Tuesday's game, Los Angeles manager Mike Scioscia didn't seem to have a problem with Hamilton sliding headfirst.
"It's part of his instinct to get to a base," Scioscia said. "Sometimes you just react to a situation. It's just competitive nature, and Josh plays hard."
A five-time All-Star, Hamilton has struggled since signing a $125 million, five-year contract with the Angels before the 2013 season. He hit a career-low .250 last year with 21 homers and 79 RBIs, his poorest power numbers since 2009. He was batting .207 with 25 RBIs through June 23, then hit .289 with 54 RBIs during the rest of the season.
Hamilton strained a calf muscle during a baserunning drill on Feb. 25 and didn't play in his first spring training game until March 17. He is hitting .444 with two homers and six RBIs in 27 at-bats this season.