(CBS) Cubs right-hander Jake Arrieta is undergoing an MRI on Tuesday afternoon after exiting with a cramp in his right hamstring in the third inning of a loss to the Pirates on Monday afternoon.

The Cubs are attempting to gain clarity on whether Arrieta’s ailment was simply a cramp or a bigger problem. Arrieta’s next start — scheduled for Saturday against the Brewers — is now expected to be pushed back, manager Joe Maddon told reporters in Pittsburgh late Tuesday afternoon. However, that’s not yet official.

Arrieta has said he doesn’t believe the injury to be “serious,” though the MRI results will finalize that question.

Earlier Tuesday, Maddon spoke to the difficulty of weighing a player’s desire to fight through an injury in the playoff race and protecting said player.

“Especially with veteran players, I’m going to listen to these guys, and I’m going to give them the benefit of the doubt,” Maddon said in an interview with Matt Spiegel and Danny Parkins on 670 The Score. “I do trust them, but I want to hear what they have to say first before making a decision.”