According to the Elias Sports Bureau, McDonald is the first Pirate since 1900 to allow three or fewer runs in each of his first 14 starts on the season.
"He just comes down and deals," teammate Andrew McCutchen said. "He gives us a chance to score some runs, then keeps us ahead the whole game. He's grown. He's going out there and doing a good job."
McDonald will look to keep up that pace on Wednesday against the Phillies at Citizens Bank Park.
In his previous start, on Thursday against the Twins, McDonald tossed his first career complete game, allowing just one run on six hits and striking out five. He improved to 6-3 on the season with a 2.19 ERA.
"It's nice to get one. It's something we've talked about," manager Clint Hurdle said. "Moving forward, we'll let everyone know he's done it. I'm sure he'll let everyone know he's done it -- and rightfully so."
Meanwhile, the Phillies are expected to use their bullpen to get through Wednesday's contest after playing a doubleheader against the Rays on Sunday.
After Cole Hamels and Cliff Lee were used in the doubleheader, a likely option is reliever Raul Valdes, who last pitched on Saturday and tossed two innings, surrendering only one hit.
On the offensive side, the Phillies will be happy to welcome back second baseman Chase Utley, who appears ready to return.
In his final rehab start with Triple-A Lehigh Valley on Tuesday, Utley belted a home run and finished 2-for-5.
"So far, so good," Utley said after the IronPigs' 10-3 win. "I'm looking forward to moving forward. I'll talk to [general manager Ruben Amaro Jr.] and tell him how I feel and go from there. Right now I feel good. Everything so far has been pretty good. I got a few pitches to hit, put some decent swings on the ball. And there you go. I felt like I got a few kinds of balls defensively and made out OK. So in my mind that's a positive. I'm feeling pretty confident. I felt a little bit more comfortable out there on the field and in the batter's box, and hopefully I'll move forward from here."
Pirates: Barajas unlikely to go on DL
Though neither Rod Barajas nor manager Clint Hurdle think the bone bruise in Barajas' left knee will put him on the disabled list, the catcher will likely be on the bench for a few days.
To deal with Barajas' absence, the Pirates optioned first baseman Matt Hague to Triple-A Indianapolis on Tuesday and called up catcher Eric Fryer. To make room for Fryer on the 40-man roster, left-hander Daniel Moskos was designated for assignment.
"We don't think he'll be a DL candidate," Hurdle said. "But we do have a bone contusion to deal with; sometimes they respond sooner than later. But we're in a position now where every game matters, and I don't think it would be fair to Rod or to our club to carry one catcher through this period."
Phillies: Howard could be back after All-Star break
First baseman Ryan Howard will return to Philadelphia on Wednesday for "functional testing on his left Achilles", the team announced on Tuesday. If Howard passes all those tests, he will begin a rehab assignment with Class A Lakewood on Thursday.
Once a position player begins a rehab assignment, he has 20 days before he must be activated unless there is a setback. So if Howard takes the full 20 days, he could be back no later than July 18, six games following the All-Star break.
Howard has been on the DL since the season started after undergoing surgery on the Achilles in October. He also suffered a setback because of an infection in the heel in February.
"More than likely, the way things look, [he'll be back] after the All-Star break," manager Charlie Manuel said. "He feels real good. He still says that when he runs he's got a little limp. He says, 'I want to play, and I feel like I can play.' He says, 'I don't know if I'll be where you want me to be or not,' but at the same time, he's got to be able to go play and be able to do some things. He feels like he's getting there. He's very positive about where he's at."
The Phillies are 12-5 against the National League Central this season, the highest winning percentage against that division for any NL club this season.
Pirates third baseman Pedro Alvarez has gone 15-for-34 with five home runs, three doubles and 10 RBIs in his last 10 games.