On Thursday morning, Upton sounded like he would be fine.
"Last night it just wouldn't loosen up for me," Upton said. "I went back out for the top of the fifth, the trainers did a little work on me between innings and I felt OK. But once I got back on the turf it kind of tightened up, you know."
Upton did not start on Thursday in the finale against the Mariners.
"Today, I feel good enough to come off the bench," Upton said. "Joe didn't want to start me today. But I feel good enough to come off the bench.
"I plan on being in the lineup [on Friday]. It's not that big of a deal. Precautionary measure, and that's about it."