Hamels will undergo an MRI on Monday to determine the extent of his oblique injury, Jordan Bastian of MLB.com reports.
Hamels was scheduled to have an MRI on Saturday, but the Cubs will instead wait a couple days, and provide treatment in the meantime. The full extent of Hamels' injury will not be known until doctors review the results of Monday's scan, so it remains to be seen just how long he will be out.