With the victory, which came in front of a sellout crowd at Nationals Park, St. Louis sits one win away from claiming the best-of-five series and moving onto the NL Championship Series.
"Game 3, when it's 1-1, is obviously a pivotal game," Matt Holliday said after his three-hit day. "This was a good win, but we still have work to do."
Having pitched only 17 regular-season innings, Carpenter nevertheless took the mound in the October setting that typically yields his best. Wednesday's outing wasn't pristine, yet plenty sufficient to send the right-hander to a franchise-best 10th postseason win.
Carpenter skirted around trouble during a 25-pitch first inning and took the mound in the second already staked to a 4-0 lead. Consecutive two-out hits by Holliday and Allen Craig drove home a first-inning run. Kozma then connected on a first-pitch fastball from Nats starter Edwin Jackson for a three-run blast in the second.
"I was just looking for a pitch in the zone," said Kozma, just two games removed from fielding questions about his game-changing error. "[I] put it out in the outfield."
Carpenter, 13 years Kozma's elder, finished the thought.
"Went over the fence," Carpenter said.
The Nationals managed to send the tying run to the plate only once the rest of the day, and Carpenter thwarted that attempted rally by getting Michael Morse to fly out with the bases loaded in the fifth. It was the 30th pitch of the inning for Carpenter.
"Being able to play behind that guy -- he's the fiercest competitor I've ever played with," Daniel Descalso said of Carpenter. "He was made to pitch in games like today."
The right-hander had been more efficient in the three previous innings, working around one hit in each of them.
"No matter if I've got one start, no starts or 35 starts, the bottom line is, you go out there on the mound and make pitches and eliminate all of the distractions," Carpenter said of his abbreviated season. "I was able to do that, for the most part, today."
Though Carpenter's pitch count sat at 89 after the fifth, manager Mike Matheny sent the veteran back out in the sixth. Carpenter, who had not thrown more than 92 pitches in any of his three September starts, finished the game at 106. He retired two batters in the sixth, which was closed out by hard-throwing rookie reliever Trevor Rosenthal.
Rosenthal pitched a perfect seventh, too, and was the first of three relievers to preserve the win for Carpenter, whose last victory came 349 days ago in Game 7 of the World Series. In between, he had to be shut down twice due to weakness and numbness in his throwing arm. That led to a summer diagnosis of thoracic outlet syndrome and subsequent surgery -- one that was supposed to have ended Carpenter's season.
The journey wasn't lost in the moment on Wednesday either.
As Carpenter stepped to the plate in the second and heard home-plate umpire Joe West remark about how perfect the day was for baseball, Carpenter took a step back to reflect.
"This is what you play for," the right-hander said. "I took it in a little bit. Yeah, no question."
Then Carpenter went on to put the Cardinals on the cusp of advancing to the NLCS for the fifth time in the last nine seasons.
"It's hard to believe not too long ago that they took a rib from this guy," Matheny said. "And as soon as they did, he was still talking about how he was going to help this club. ... [It's] just beyond words the amount of respect that everybody in that clubhouse has for him."
"Some pitchers, I'm sure, would have taken off and gotten ready for next year," added David Freese. "He's an animal out there. For him to take the ball like he did today in a crucial game like this and do what he has always done, that's special."
Support behind Carpenter was aplenty, led by Kozma's third career home run. It was here at Nationals Park, on Aug. 30, that Rafael Furcal's season ended with an elbow injury. Kozma was summoned from Triple-A the next day and has since assumed the starting job at short.
Jackson, a member of the Cardinals' 2011 World Series championship club, was battered throughout his five-inning start. Sitting successfully on Jackson's four-seam fastball, the Cards recorded eight hits off him.
"The Cardinals were coming out and being aggressive," Jackson said. "They are not waiting around for you to get strike one. They're coming up, getting pitches early in the count."
St. Louis then piled it on against a laboring Washington bullpen. Freese doubled and scored on Descalso's sixth-inning sacrifice fly. Yadier Molina drew a bases-loaded walk in the seventh, which began with consecutive singles by Jon Jay and Carlos Beltran.
Jay and Beltran connected for back-to-back two-out hits in the eighth, and both scored on Holliday's two-strike single.
The Cards have clobbered Nats pitching for 27 hits and 20 runs in the last two games, and they will face a pitcher in Game 4 (Ross Detwiler) that they chased from a Sept. 30 start after 2 1/3 innings. In return, the Cardinals will counter with their 2012 ace -- Kyle Lohse.
"When everybody's clicking, we're dangerous. I think everybody knows that," Freese said. "We're feeling good right now, but we're going to get some sleep today, turn the page and come ready to go just as focused as we have been."