The 28-year-old righty followed through on that on Saturday, allowing just two hits and a walk over four innings for Double-A Altoona. He threw just 38 pitches and will make his next rehab start for Triple-A Indianapolis on Thursday -- which is set for five innings and 80 pitches.
"Very efficient," Pirates manager Clint Hurdle said. "We just got to see both ends of the ruler [with the two starts]."
McDonald threw all four of his pitches on Saturday and only had one three-ball count. His fastball sat at 88-92 mph, and Hurdle called the start a "step in the right direction." McDonald has been on the disabled list since May 7 with stiffness in his right shoulder.
It is worth noting that the Pirates have him on a similar pitching schedule as Jeanmar Gomez, who started on Sunday against the Reds and replaced McDonald in the rotation last month.
Charlie Morton is also on that same five-day path. He underwent Tommy John surgery last June and hasn't pitched for the Pirates since, but was scheduled to throw five innings and 80 pitches in a rehab start on Sunday for Triple-A Indianapolis. Hurdle said Morton will focus on nailing his sinker and four-seam fastball, in addition to throwing his curveball and changeup.
When Morton and McDonald have completed their rehab assignments, Hurdle will have a difficult decision to make. Gomez (2-0, 2.30 ERA heading into Sunday) began the year as a long reliever, often mopping up the middle innings for Jonathan Sanchez, but has done all he can to stay in the rotation.
He hasn't allowed more than three runs or five hits in any of his six starts, although he's eclipsed five innings just once -- a seven-inning, three-hit performance against Detroit on Tuesday. The Pirates are 6-0 in games he's started.
Hurdle last discussed the topic a week ago, saying he won't have to worry about it until the time comes. That time is coming, however.
"Whatever decision they make is good for me, bullpen or a starter," Gomez said. "For me, I just have to be ready. I have to prepare for any situation, starter or reliever."
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. Steven Petrella is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.