As it turns out, Barthmaier's stay is going to last a bit longer.
The 24-year-old was activated on Friday and will step into the rotation spot left vacant by Tom Gorzelanny, whose season has ended because of a sprained ligament in his left middle finger. As a result, Barthmaier is scheduled to pitch on Tuesday, though he would be able to step in at any point earlier if necessary.
Barthmaier's last outing came on Aug. 30, when he pitched 6 2/3 innings for Triple-A Indianapolis. He has been at his offseason, Atlanta-area home since.
"I was a little disappointed when I didn't get called up in September," said Barthmaier, who was already on the team's 40-man roster. "But this is a great opportunity to give a better impression than the last time."
Barthmaier was not one of the 10 players called up on Sept. 2 because he has been slated to participate in the upcoming Arizona Fall League season, and management saw no reason to increase his innings load any further.
There is no official word yet on what this change in schedule will mean for Barthmaier's AFL plans.
Barthmaier's only other taste of the Majors came on June 27, when he made a spot start that lasted just 2 1/3 innings. He allowed seven earned runs on two walks and seven hits in that outing and was sent back to Indianapolis the following day.
As for McCutchen, he will stay with the team just through Sunday.
"He's just here to kind of observe and get a feel for Pittsburgh and the clubhouse," manager John Russell said. "We just thought it would be a nice thing to let these guys be around the staff, be around the players and kind of set them up for the offseason, to make sure that their offseason program is put together."
Both center fielder Andrew McCutchen and Neil Walker are scheduled to come in for the same three-game stint on Monday.
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.