Behind the plate, Michael McKenry guided the tall right-hander through six innings of two-hit shutout pitching. And at bat, Andrew McCutchen furthered Pittsburgh's only productive rally with a key single.
"He was pitching against a very good club, and on the road," said Pirates manager Clint Hurdle, seeing a payoff for his enduring confidence in McDonald. "That was an impressive outing. And a huge step forward for us; we're going to need him for us to get something done this year."
In virtually their first head-to-head encounter to vouch for their legitimacy as postseason contenders, the Pirates responded to push the third-place Cardinals two games behind them in the National League Central standings.
His recent struggles, most notably the inability to hold onto a 7-1 mid-game lead against San Diego in his last start, and the challenge represented by the Cardinals mashed up into a sizable chip on McDonald's shoulders.
At least, that was the impression of McKenry by the time he had finished warming him up in the bullpen before the game.
"He did take that out there with him," McKenry said. "He set a tone for the entire series for our staff. In the bullpen I told Mac, 'You're a leader. Go lead.'"
As he was scaling the dugout steps to take the mound in the bottom of the first, McDonald heard some more advice.
A.J. Burnett gave a little nod toward the field and said, "Hey, have fun."
"And I thought, 'Why not? Just go out there and play baseball, instead of thinking too much and making it more difficult than it is.' So that's what I did," McDonald said. "Just went back to that mind frame of competing, not trying to please this person or that."
After McDonald (11-5), who threw just 87 pitches, was sacrificed for a pinch-hitter during an aborted rally in the top of the seventh, the Pittsburgh bullpen had to validate his gem.
Chris Resop was first out and he matched the hits allowed by McDonald within his first two batters: Carlos Beltran singled and David Freese doubled him to third. After an innocuous flyout, Tony Cruz's grounder scored Beltran to make it a 2-1 game. But Juan Cruz entered to retire Rafael Furcal on an inning-ending infield pop, and Jason Grilli and Joel Hanrahan, pocketing his NL-leading 34th save, kept the final two innings quiet.
Whether merely an interruption of his skid or the beginning of a turnaround, McDonald walked three and struck out seven in, by far, his best of seven second-half starts. The irony was that he could have used the six runs the Bucs had averaged in the prior six, all but one defeats.
The Pirates were given two runs in the top of the fourth. When it came to getting some of their own, however, they missed the opportunity. After they loaded the bases on a walk to Travis Snider and consecutive singles by McCutchen and Garrett Jones, one run scored on a Westbrook wild pitch and another on a passed ball by his catcher, Cruz.
"That's nobody's fault but my own, really," Westbrook said. "I just put myself in that situation, and that's something I can't do there. With the way McDonald was throwing tonight, that ended up being the game."
At that point, the Bucs still had runners on second and third, no outs and Westbrook rattled. Jones broke for home on a comebacker by Pedro Alvarez and was erased, then Clint Barmes' second double-play grounder of the night ended the promising inning.
The Pirates thus went on to win a game without driving in a run for the first time since June 20, 2008, when they downed the Blue Jays, 1-0, with that run scoring on a 12th-inning error.
The heat remained high on McDonald, who had slumped to an 8.71 ERA in six prior starts since the All-Star Game break. And McDonald stood tall under it, rekindling memories of the guy who had a 9-3 record with a 2.37 ERA before that break.
"He pitched pretty well," said the Cardinals' Matt Holliday, who was hitless in three at-bats against McDonald in an 0-for-4 evening. I think he has a good breaking ball. His command was better than it's been lately. I know he's struggled with it lately, but he pitched well tonight."
Due to a rotation juggled for his benefit, McDonald was working on six days' rest. But there had to be more to the dramatic turnaround than merely two extra days to prepare.
Maybe he was liberated by the realization that he could make an errant pitch, have it creamed -- and still come away unscathed. That happened at the very outset of the game, when Jon Jay led off with a five-pitch walk and Allen Craig, who already has a Pirates-killer history, followed by teeing off on an 0-and-2 pitch.
But Craig's smash just to the right of the second-base bag found second baseman Jordy Mercer positioned up the middle, where he routinely fielded the ball and began a double play.
The Cardinals did not have another baserunner until Craig doubled with one out in the fourth. That threat was erased when Craig tried to advance on a pitch that barely eluded McKenry, who pounced on the ball to nail the runner sliding into third.
The Cardinals did not get another runner into scoring position until McDonald was out of the game.