Morton returns to the rotation in place of Vance Worley, who moves into a crowded bullpen.
"We followed up on how he's feeling [following Friday's throwing] -- and we're giving him the ball," manager Clint Hurdle said of Morton. "Vance could either piggyback Charlie's start, or play a role out of the bullpen."
Following his latest sideline work, Morton had said it seemed clear to him the club wanted to keep his arm ready "in case someone gets hurt, or starts to struggle real bad."
That did not turn out to be the case. Worley won his last start, Wednesday in Philadelphia. Since being recalled from Triple-A Indianapolis and joining the rotation on June 15, his seven wins are tied for the team lead, with Edinson Volquez and Jeff Locke.
"He's earned an opportunity. It is what it is," Worley said. "I deserve a spot, too, so instead of taking me out of the equation completely, they put me in the 'pen. We'll see how things go. Hopefully [Morton] does well, because he's a reason we're here, too."
Tuesday's start at PNC Park will be Morton's first since Aug. 15. For the season, he is 5-12 with a solid ERA of 3.84.
"We'll give Charlie the ball, see where he can take that, and evaluate afterward on what we do next," Hurdle said.
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.