"As I started my drive to the plate, it grabbed pretty good," Arrieta said after the 12-0 loss. "As I tried to throw a warm-up pitch, it just wasn't going to happen. ... It could have been a lot worse. No pop or anything like that."
Although he doesn't believe the injury in serious, and is hopeful he won't miss a start, Arrieta had an MRI on Tuesday so the club would have a better read as to the extent of the injury.
Arrieta gave up three runs, including two home runs, before leaving. It was his worst start in almost two months; he was just named pitcher of the month for August after posting a 1.21 ERA over six outings. The Cubs are already using a six-man rotation, so they have the depth to be careful with Arrieta.
"He kind of got a cramp in his right hamstring," manager Joe Maddon said. "We'll see how it plays out. He was able to loosen up."
Arrieta exits early with apparent leg injury
Jake Arrieta is removed from the game in the third inning after suffering an apparent right leg injury against the Pirates.