"[He's] limping, but OK," manager Jim Leyland said. "It looked like an ankle bruise. He got checked out by the doctors. He's sore, limping a little bit, but he should be fine."
Galarraga had a solid start going in holding down the Red Sox until Marco Scutaro homered with one out in the fifth inning. After Jed Lowrie lined softly to short, Youkilis centered a ball and sent it back up the middle with authority. The ball hit Galarraga as he was following through on his delivery, and he had no time to react.
"I didn't see it when it came," Galarraga said. "I saw it when it was close to me. It was tough to see, because it was so low. I'm trying to catch the ball, and it's a split second you have."
The impact could be heard from the press box atop Fenway Park. Galarraga lay on the ground for several minutes while head athletic trainer Kevin Rand attended to him. He eventually stood up on his own power and walked off the mound, but there was no question he was heading out of the game.
The fact that Galarraga was walking was a good sign. He said he knew by then it wasn't bad.
"I think I knew in the beginning, when it happened," Galarraga said. "It was pretty sore, but I knew I could put my foot down, so I made me a little more relaxed. If it was something bigger, I don't think I would've been able to walk off like that."
Former Red Sox pitcher Enrique Gonzalez eventually got the last out of the inning and stranded Youkilis. Galarraga finished with a run allowed on five hits over 4 2/3 innings, one out shy of qualifying for the victory.
The injury doesn't appear to be long term, which is good news on the club's injury front for a change. Detroit is already missing Magglio Ordonez, Carlos Guillen and Brandon Inge from the starting lineup, and it had to use a spot starter Wednesday with Eddie Bonine. With a day-night doubleheader coming up Tuesday against the White Sox, the Tigers are stretched thin enough that Jeremy Bonderman is expected to pitch Tuesday, then Saturday on short rest.
"Because Bondo is coming back to the rotation," Galarraga said, "it's probably going to give me one more day."
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.