McDonald was tagged with eight runs (three earned) on eight hits in just 1 2/3 innings of work. The right-hander absorbed the loss, falling to 1-2 on the season.
"There wasn't anything real crisp," manager Clint Hurdle said. "The execution -- the lack of it -- he just couldn't get the ball where he wanted to get it and couldn't repeat it, and it was hard. It was hard out there for him. Too many pitches up and over the plate against a very good hitting team."
"I left the ball up and got behind guys," McDonald said. "Good teams and good hitters are going to hit those pitches; when you make mistakes, they are going to make you pay. I didn't keep my team in the game today, and that's what happens when you make bad pitches: You get hit hard."
It was McDonald's shortest outing since he went 1 2/3 frames for the Dodgers against San Diego on April 30, 2009, when he allowed three runs on two hits and walked four.
Cardinals starter Lance Lynn battled through five innings and allowed four runs on seven hits. The right-hander picked up the win, upping his record to 2-0.
"I was throwing the ball pretty well, and then I made a mistake to Walker," Lynn said, referring to Neil Walker, who hit his first homer of the season in the third. "He hit a home run on a pitch that didn't do what it was supposed to do. You tip your cap to him. I was able to get through the next two innings.
"I wish I could have gone deeper. When you have a 10-run lead, you're trying to get quick outs and not have long innings. I wasn't able to do that either. I think that was the most frustrating part."
McDonald's first-inning woes continued as the Cardinals nicked him for a run. Jon Jay led off with a single, and Matt Carpenter beat out an infield single. Matt Holliday hit a drive off the top of the Clemente Wall in right field. Jay and Carpenter stopped at second and third, and Holliday was tagged out in a rundown between first and second. Allen Craig then bounced into a fielder's choice, with Carpenter being tagged out at third as Jay scored.
McDonald's velocity was down a few ticks, leading to questions about his health.
"I don't want to speculate right now," Hurdle said. "I haven't had any conversations with him, so I'm probably not going to have any answers for you along those lines tonight. I need to sit down and really talk to the guy. I haven't seen anything glaring, but we saw what you saw as far as velocity, finish and command. There were some challenges out there for him, a number of them for him."
The Pirates bounced right back in the bottom of the first against Lynn. Starling Marte doubled, extending his hitting streak to nine games. Travis Snider drew a walk. With one out, Garrett Jones delivered an RBI single, driving in Marte and tying the game, 1-1.
But the Cards got to McDonald again in the top of the second. David Freese drew a walk with one out, and Pete Kozma doubled. Jay stoked a two-out, two-run double, knocking in Freese and Kozma. Carpenter drew a walk, and Jay scored on a throwing error by shortstop Clint Barmes. Craig tagged a two-run double off the wall in center and was driven in by Carlos Beltan with an RBI single.
Yadier Molina then doubled, scoring Beltran and knocking McDonald out of the game. He was replaced by lefty Justin Wilson.
When the smoke cleared, the Cardinals had batted around and owned an 8-1 lead thanks to seven runs, just two of which were earned.
"It was balls up in the zone," McDonald said. "You leave balls up in the zone, good hitters are going to hit them hard. I threw a lot of bad pitches and didn't hit my spots, and they made me pay."
The Cards' onslaught continued in the top of the third against Wilson. After two walks, Holliday doubled to right-center, giving the Cardinals a 10-1 lead.
The Pirates cut the Cardinals' lead to 10-4 in the bottom of the third inning when Snider walked and scampered home on a double by Andrew McCutchen with one out. Walker then clubbed his two-run homer. Pittsburgh added two runs in the eighth, but it was not enough.
"They've always done that," Cardinals manager Mike Matheny said of the Pirates' threatening late. "They do that here especially. They play at home in the late innings especially well. That's a conversation we're having in the dugout. We have to keep pushing. We have to keep scoring. Don't begin to take anything for granted, because this team can sneak up on you, and obviously they did it last night. But we know they can do it. We've seen it firsthand."