The Cardinals and pitcher Michael Wacha both agree he's struggled.

"He wasn't necessarily overly excited about how the ball was coming out of his hand," manager Mike Matheny said Friday after announcing the 23-year-old right-hander will be pushed back in the rotation. "So what do you do? You stick to the original plan, and we just stopped."

Rookie left-hander Marco Gonzales, who has backed up Wacha's two abbreviated starts, gets the start instead on Sunday.