The last time Mock pitched in the big leagues was on June 8 against the Giants. It was his Major League debut and it was an outing he would like to forget. He didn't get past the fifth inning as the Nationals lost to the Giants, 6-3, at Nationals Park.
The team hopes this next outing is a different story.
"He'll come over here and he will not have the nervousness of the first start. Hopefully, he will feel more at home and give us a solid outing," manager Manny Acta said.
Mock is replacing left-hander Odalis Perez, who is on the disabled list because of tendinitis in his left shoulder.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.