Yankees manager Joe Girardi said that Britton suffered the injury -- between his ninth and 10th rib on the left side -- while warming up on Thursday afternoon. Britton is expected to have an MRI performed in New York.
"We shut him down when he was warming up last night," Girardi said. "He called and we had to shut him down."
Britton, 25, has been on the shuttle all season between the big leagues and Triple-A Scranton/Wilkes-Barre and was in his fourth stint with the Yankees, though he has appeared in just four games (0-0, 1.29 ERA in seven innings). He last appeared on Tuesday vs. Toronto, allowing two hits in a scoreless ninth inning.
Giese, 31, was recalled from Triple-A on Tuesday and threw 3 2/3 innings of one-run, five-hit relief behind Joba Chamberlain's first Major League start. He was optioned back to Scranton/Wilkes-Barre on Wednesday to make room for catcher Jorge Posada on the Yankees' roster, but can be recalled without the customary 10-day waiting period because the roster move deals with Britton's injury.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.