The Phillies have demoted rookie right-hander Mick Abel, who has struggled since he struck out nine in his major league debut, to Triple-A Lehigh Valley and returned Taijuan Walker to the rotation.

Phillies manager Rob Thomson called Mick Abel into his office Friday morning and let him know he was being optioned to triple-A Lehigh Valley. “I think he understood,” Thomson said. “And I think he’s going to go down there,

Walker will start Tuesday at San Francisco. He could pitch four innings or so. Then, during the All-Star break, the Phillies will reassess.