Arrieta's next start will be pushed back even if the results of the MRI on his injured hamstring are promising, Gordon Wittenmyer of the Chicago Sun-Times reports.

It doesn't sound like he'll pitch in this weekend's series against the Brewers, even though it's possible he is not dealing with a major hamstring injury. Mike Montgomery will likely start Saturday with Kyle Hendricks starting Sunday on normal rest. Arrieta could conceivably return to the rotation next week against the Mets.