Schumaker's first career pinch-hit home run and fourth home run of the season came off Pirates reliever Matt Capps, who came on in relief of Duke with a 3-2 lead.
"It was my first pinch-hit home run," Schumaker said. "It came at a good time. It was a big moment, and I haven't had too much success off Capps -- I don't think anybody really has. He's a really good pitcher and I just tried to stay on top of his fastball and I ran into one."
Capps was ejected for hitting the next Cards batter, Albert Pujols.
"I think he read it exactly right," La Russa said. "I think it was an intentional hit and there is no doubt in my mind it came from the bench, and I really believe it didn't come from the manager. Don't ask me to expound on that."
Capps indicated that hitting Pujols was not intentional.
"It's Albert Pujols," Capps said. "He's the classiest guy in baseball. He's not somebody that you're intentionally going to hit, especially not in that situation. We were playing a good game. Yeah, I understand that I just gave up the homer, but I had him 0-1, tried to go in, I got too strong with it and it got away."
Jesse Chavez replaced Capps, and gave up a single to Matt Holliday and a two-run double to Ryan Ludwick. Khalil Greene delivered a RBI single, bringing the Cardinals' tally to five runs in the eighth inning.
Duke tossed 7 1/3 innings, allowing three runs, two earned, on seven hits. He received a no-decision. Capps took the loss, falling to 2-7.
Cards starter Joel Pineiro got the win, upping his record to 10-9. The right-hander gave up three runs on nine hits and recorded six strikeouts in seven innings of work.
"It was amazing," La Russa said of Pineiro's performance. "Early on, he was getting the ball in the middle and not a lot of sink, and they were pounding him. Then those last three or four [innings], he was sharp as nails, and that's why he's got one of the league's best ERAs. He hung with it and hung with it, and all of the sudden, he got it all together and was outstanding."
"It just one of those things," Pineiro said. "You never get down on yourself. I gave up those couple of hits early, but I was able to settle down when I had some runners on base. With the offense that we have it was just a matter of one inning or a couple of hitters come through. I just stayed positive and kept working hard."
The Pirates jumped out to a 2-0 lead in the bottom of the second. First baseman Steve Pearce cracked a two-run home run, his second of the season.
Pittsburgh made it 3-0 on a Delwyn Young RBI single in the third inning.
The Cards got on the board in the top of the fourth inning. Julio Lugo singled; he advanced to third on an errant pickoff thrown by Duke. Holliday lofted a sacrifice fly to center field, slicing Pittsburgh's lead to 3-1.
St. Louis trimmed it to 3-2 in the top of the seventh inning. Duke had Holliday, who singled, picked off first, but Pearce threw the ball into center field, allowing Holliday to go to third base. Holliday scored on a Yadier Molina RBI single.
Kyle McClellan picked up his second save with 1 2/3 innings of scoreless relief for St. Louis.
The Cardinals are now a season-high 11 games over .500.
"We need to win every game," Schumaker said. "We're in a pennant race, and we feel like we have the pitching and the offense to do it now."