"I just slipped and I don't know if it was concrete or a drain or whatever down in the corner, and my front foot slipped and twisted my back knee," Sweeney said. "I felt it pull kind of on the outside and it started to tighten up on me and I kind of got a little scared. They wanted me out of the game to make sure I was OK."
Sweeney had a brace on Monday and hoped to be able to take part in all the drills. After a lot of ice Sunday night, there was still some soreness Monday.
Last year, Sweeney crashed into the outfield wall in Seattle and fractured his ribs.
"It's always the freak things that happen," he said. "Going after a ball in the outfield seems to be the main one. Running after it, you think, 'I'm going to cut this ball off and throw it in.' You don't think you're going to slip. It happens. I should be OK."
So he's not ready to switch and be strictly a DH?
"No, not at all," Sweeney said.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.