ST. LOUIS -- With fans screaming at him to send in a pinch-runner for lead-footed catcher Yadier Molina, St. Louis manager Mike Matheny left him at second base.

Some of the same fans also might have wondered why Matheny allowed center fielder Peter Bourjos to hit with the game-winning run in scoring position in the ninth inning of a scoreless game.

Both dice rolls turned up seven when Bourjos' two-out single scored Molina and the Cardinals wrapped up a three-game sweep of Pittsburgh with a 1-0 victory Wednesday at Busch Stadium.

It was just the second walk-off hit for Bourjos, who entered the game hitting only .233 and had lost his starting job twice during the season.

"I think so," Bourjos said when asked if it was the biggest hit of his career. "At this point, we're leading the division and this is a big game."

Bourjos got his chance to hit when Molina drew a walk off closer Mark Melancon (2-4), pitching a second inning for the first time in 61 appearances. Right fielder Jon Jay singled Molina to second.

On an 0-and-1 pitch, Bourjos grounded a cutter up the middle and third base coach Jose Oquendo didn't hesitate to wave in Molina. Andrew McCutchen's throw home was strong but off-line to the left and Molina slid home as the crowd of 42,864 erupted.

Matheny didn't give a second thought to running for Molina.

"It might be a different conversation if he gets thrown out at the plate, but I'd still give you the same answer," Matheny said. "To me, his value behind the plate in that situation outweighs what we might give up on the bases."

St. Louis closer Trevor Rosenthal (2-6) worked around second baseman Neil Walker's leadoff hit in the ninth, wiping him out when catcher Russell Martin bounced into his second double play of the day.

Bourjos' heroics gave the Cardinals (76-63) a five-game winning streak and a 2 1/2-game lead in the National League Central over Milwaukee, which played Wednesday night at the Chicago Cubs.

The Pirates (71-68) dropped five games off the pace.

In a September game that was played with October intensity, both starting pitchers were lights-out and tensions were high.

Both benches exchanged insults before the bottom of the sixth, moments after St. Louis starter Shelby Miller buzzed a first-pitch fastball behind McCutchen.

The pitch, perhaps in response to Pittsburgh's Edinson Volquez plunking left fielder Matt Holliday and Matt Adams in succession in the fourth, drew immediate warnings from plate umpire Ron Kulpa.

Pirates manager Clint Hurdle called Miller's pitch "an ambush and a cheap shot."

"He took his one shot and he missed," McCutchen said of Miller. "(Kulpa) gave out the warnings and that was it."

Miller and Volquez didn't miss too often, shutting down the opponents' lineup in a classic pitcher's duel. Miller went seven innings, permitting only three hits and walking three while fanning five.

Volquez lasted 6 1/3 innings, allowing three hits and a pair of walks with five strikeouts.

The bullpens decided it after that, and Melancon's first multi-inning stint since Oct. 2, 2012 came up a loser as Bourjos delivered.

"He's been swinging the bat well and he's had a real nice approach," Matheny said. "Peter's in a good place right now."

NOTES: With St. Louis RHP Michael Wacha returning to the rotation Thursday night in Milwaukee, it means that trade deadline acquisition Justin Masterson is being demoted to the bullpen. The right-hander is 2-3 with a 7.90 earned run average in six starts, only one of which was a quality start. ... Pittsburgh designated OF Michael Martinez for assignment Tuesday. Martinez managed only five hits in 39 at-bats over 28 games for the Pirates, driving in two runs. ... Cardinals 2B Kolten Wong (neck) was back in the lineup after not starting Monday or Tuesday night. He pinch-hit in both games, tying the score Monday with a two-run home run in the seventh.