PITTSBURGH -- The magic number right now for Tony La Russa is zero. That's zero games above or below .500, and the Cardinals manager views getting to that point as the current goal for his squad.

The Cards took another step toward that point on Tuesday as they took advantage of a strong performance from starter Adam Wainwright and a solid offensive game to pick up their fourth straight win, a 6-4 victory against the Pirates at PNC Park.

The win brought the Redbirds to three games below .500 for the first time since April 29. They remained six games behind the first-place Brewers.

"There have been several times where that zero has been so far away that you had to really force yourself to be optimistic," La Russa said. "Now there's a light at the end of the tunnel. It's exciting to see the zero out there not so far away."

The Cardinals inched closer to the zero mark behind a quality start from Wainwright. He limited the Pirates to two earned runs on eight hits and a walk in six innings despite having an inconsistent delivery which, in turn, led to his stuff being off for much of the game.

"I struggled all night, I just had to battle and try to get outs with what I had," Wainwright said. "My slider was absolutely terrible and I couldn't keep my fastball down consistently. I just had to make good pitches when I had to."

Wainwright was able to do that in the second, fourth and fifth innings, when he gave up seven hits and a walk, but avoided serious damage by not giving up an extra-base hit. He gave up both runs on RBI singles to eight-hole hitter Jack Wilson and was upset with himself for leaving hittable pitches in the zone with the pitcher on-deck.

"I'm trying to make those balls out of the strike zone with the pitcher on-deck, almost pitch around him," Wainwright said. "I hung both of them and he's a professional hitter, he's going to make the plays."

But those were the only key mistakes Wainwright made, and he put the Cardinals in a position to win. From there, an opportunistic offense gave him all the support he needed.

The key blow for the Cards came courtesy of two mistakes by Pirates catcher Ronny Paulino in the sixth. After Scott Rolen singled with two outs, Ryan Ludwick hit what looked to be an easy popup to Paulino. But the catcher couldn't make the play, and the inning lived on.

"It was very high, if you're in the big leagues, fans think you should catch it and you probably should, but it wasn't a routine popup," La Russa said.

Ludwick took advantage of the opportunity given to him and doubled to drive in Rolen, who slid home safely when Paulino couldn't handle the relay throw from Wilson. The Cards went up for good, 3-2.

"I'm just glad I got the second chance and I made the most of it," Ludwick said.

The Cards padded their lead with some good situational hitting in the seventh. Aaron Miles singled and pinch-hitter Chris Duncan doubled to lead off the inning, and both scored on back-to-back sacrifice flies by David Eckstein and Skip Schumaker to extend the lead to three.

The Pirates threatened for the last time in the bottom half of the inning when they plated a run on three straight one-out singles against Russ Springer. The Bucs had two runners on and the speedy Nate McLouth the go-ahead run at the plate, but left-hander Randy Flores relieved Springer and needed just two pitches to induce McLouth to ground into an inning-ending double play.

Flores shrugged off the efficiency of the outing and said he was fortunate McLouth's grounder was hit exactly where it was.

"Those can just as easily go bad in two pitches," Flores said. "It was fortunate to be hit at the right spot. If it's a foot or two to the left, maybe it's an infield single."

As Flores slammed the door, the Cardinals kept a winning streak alive that is beginning to breathe some life into the Redbirds' playoff hopes that had seemed fleeting days ago.

"We're playing better and we need to feed off this a little bit, like we've been doing," Wainwright said. "We had some really really good wins in the last series we played. For us to come in and win the first game here is momentum, hopefully, to just keep it going.

"I think we've just not been playing good all year long and we're finally starting to click a little bit," he added. "Hopefully, we keep it going, because we're too talented to let this season go down the drain."