Upton tested his leg when he arrived at Safeco Field hours before game time on Wednesday and spoke of the big test to see if he could play.
"Just change of direction, being able to push off it," Upton said. "It felt fine."
Upton said he is not in a situation where he will be holding back any effort, but he did say they will have to keep an eye on his leg for the next couple of days.
"Especially with the cold weather coming up -- probably going to have an issue with keeping it loose," Upton said. "That's the biggest thing is keeping it loose. Like I said, we'll keep an eye on it and see how it feels day to day."
The Rays play an afternoon game at 4 p.m. PT (7 p.m. ET) on Thursday and Upton expects to play.
"We'll see how I feel," Upton said. "It's a 4 o'clock game, so it's really not too much of a day game. ... We'll monitor it again tomorrow morning and see how it feels."
Rays manager Joe Maddon planned to keep a close eye on his center fielder Wednesday night.
"I want to see him," Maddon said. "I'll see how he feels tomorrow. We'll just watch him all night long. I don't want to push him right now. We have a couple of day games coming up after night games. We'll just see how he comes through tonight and we'll evaluate it again tomorrow."
Upton said he was happy to be back on the field.
"I'll do anything I can do to help this team win," Upton said. "But I can't do it when I'm not on the field. So I'm glad to be back out there and hopefully we can do some things the rest of this road trip."
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.