Arrieta tried to throw a practice pitch to see if he could continue in the game but stopped quickly without even throwing the ball. He walked off in severe pain with the trainers and manager Joe Maddon as his day ended after 2 1/3 innings and giving up three runs including two homers.

He had a 1.59 ERA in nine starts since the All-Star break which is lowest in the majors and was named National League Pitcher of the Month for August.

Cubs reliever Justin Grimm replaced Arrieta.