"Initially, it felt like a little quad issue," Upton said. "Now it's kind of moved into my groin area now -- nothing to worry about -- maybe take a day or two to get back."
Upton singled in his first at-bat Sunday, moved to second on a groundout by Carl Crawford then stole third base.
"[It] felt fine," Upton said. "When I got out to the outfield it kind of locked up on me where I couldn't run."
Upton played in the field in the top of the second and said he felt lucky that no balls were hit in his direction.
"Running in a straight line wasn't really the issue," Upton said, "more moving side to side and definitely quick bursts."
Upton had treatment on his leg before the team charter took off from Tampa on Monday night. But when he went out on the field prior to Tuesday night's game, he felt he would be best not to push his luck.
Upton said when he's back in the lineup it will be in center field and not DH. He also said he did not think his injury would land him on the disabled list.
"No chance," Upton said. "Not even close to the DL."
Rays manager Joe Maddon felt confident Upton would be back soon.
"He had a good look to him today," Maddon said. "He felt confident about tomorrow."
Upton missed the first six games of the season due to the final stages of his recovery from offseason shoulder surgery. He is hitting .217 with no home runs and one RBI in seven games.
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.