Cumpton brings a 2-0 record and 1.42 ERA from Indianapolis and is ranked the 12th-best prospect in the Pirates' system.
Catcher Russell Martin was a late scratch from Wednesday's lineup, but that may not have had anything to do with manager Clint Hurdle's preference that the veteran instead be behind the plate for Cumpton. Martin would not ordinarily play a night game and then the following afternoon.
"We're trying to strategically find spots for him to rest," said Hurdle, insisting he had posted Wednesday's original lineup too soon. "I got in a hurry, before I got with him. So it makes it look bad on the player."
However, Martin was not sure of being back in the lineup Thursday.
"I'll come in and look at the lineup -- then I'll know," said the catcher.
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.