The team announced Burnett was removed from the game with one out in the fifth for "precautionary reasons" after he had already thrown 106 pitches and had walked four of the previous eight hitters.
After the game, Phillies manager Ryne Sandberg said Burnett had been dealing a "little groin irritation" for the last week, but hadn't said anything to the coaches or medical staff until the fifth inning.
"He wasn't able to get full extension on his pitches," Sandberg said. "And it got to the point where it really bothered his control."
Sandberg said it was too early to tell if Burnett would be able to make his next start, which would be Wednesday against Atlanta.
"We'll have to re-evaluate him tomorrow and see how he is, and go from there," Sandberg said.
In all, Burnett issued six walks and a wild pitch, and threw nearly as many balls (54) as strikes (52). He has now issued 12 walks in 10 innings pitched over his last two starts.