Baker was cruising against the Rays, having allowed just an unearned run on three hits and a walk over five innings. Baker also struck out three and threw 62 pitches, 44 for strikes, before being replaced by left-hander Phil Dumatrait in the sixth inning.
Baker said he started to feel discomfort in his elbow "somewhere around the third inning," and decided to tell trainers about his injury after the fifth even though he felt it was just a minor strain.
"In my opinion, no," Baker said when asked if it was serious. "At this point in the season, I'm just trying to be smart about it. I almost didn't say anything to be honest with you. I was going to continue to pitch with it. But it was just a little [more] discomfort than I'd like to continue to pitch with."
Baker, who has dealt with elbow problems in the past and had bone spurs removed this past offseason, said he knows this is a much different feeling in his elbow. He said this one is "more muscular" and is "not even close" to the feeling he had when dealing with prior elbow injuries.
Twins manager Ron Gardenhire, however, said the club will make sure it's not serious and Baker will be evaluated by the training staff on Wednesday.
"He'll get an MRI tomorrow and go from there," Gardenhire said. "We took him out as precaution. He told us he could keep pitching but we weren't going to let that happen. He felt something in his elbow."
Baker, who had been considered a candidate to be an All-Star this season, lowered his ERA to 3.01 and has 104 strikeouts in 110 2/3 innings.
He is scheduled to make his next turn in the rotation on Sunday against the White Sox in the last game before the All-Star break, but his status for that start is yet to be determined. Baker seemed resigned to missing that start.
"I guess there's never a perfect time but I think the way days work out it might allow me to have more time with the All-Star break and then rescheduling the rotation," Baker said. "But that's obviously up to them and we'll see how I feel tomorrow. But I'm confident this is just a sprain."