"It's kind of sore today (Friday) so I'm going to get an MRI real quick just for precautionary reasons," Stewart said.
Stewart was injured as he came out of the batter's box and "on to the grass" after hitting a ball to the wall in left center. He slowed up as he approached second base.
"I'll probably take it easy for a couple days, get some treatment and go from there," Stewart said.
Stewart was actually accused of loafing by his coaches before he informed them he was hurt on the play.
Stewart missed most of last season after having wrist surgery. Manager Dale Sveum claimed third base was his "job to win" earlier in spring training.
Third baseman Josh Vitters also hurt his left quad on Thursday, running the bases during drills. He was unsure if he would have an MRI but indicated it was a serious injury.
"It's just too early in camp to not be cautious," Vitters said. "Just going to do as much as I can before I get back on the field."
Vitters and Stewart join Matt Garza as spring training casualties. Garza's first batting practice session to hitters was cut short after he strained his lat last Sunday. Garza is due to resume throwing late in the weekend or early next week.