ST. LOUIS -- Trailing 3-1 with six outs left Wednesday, the St. Louis Cardinals were about to be swept by the Chicago Cubs, which would have made things even tighter in the National League Central.

However, Chicago starter Jon Lester, who dominated St. Louis for most of seven innings, left for a pinch hitter, and the Cardinals preyed on his three successors.

Scoring three runs in the bottom of the eighth, the Cardinals stole the series finale 4-3 at Busch Stadium.

"He did everything he wanted to do," St. Louis manager Mike Matheny said of Lester. "But that's why you keep grinding away -- to hopefully drive up his pitch count and get him out of there."

After permitting a leadoff triple to second baseman Matt Carpenter and a one-out RBI single to right fielder Jason Heyward in the first, Lester didn't permit another hit. He retired 20 of the last 21 men he faced, walking catcher Yadier Molina to lead off the fifth but not allowing a hard-hit ball along the way.

Even so, manager Joe Maddon sent up a pinch hitter for Lester in the eighth, ending the left-hander's day at 105 pitches. That decision, coupled with a bullpen meltdown, led to a major plot twist.

Third baseman Mark Reynolds coaxed a one-out walk from reliever Pedro Strop, and pinch hitter Greg Garcia singled. Carpenter followed with an RBI single off reliever Clayton Richard (3-1), scoring pinch runner Pete Kozma.

Maddon walked to the mound again, hooking Richard and waving in Fernando Rodney. However, rookie left fielder Stephen Piscotty foiled that strategy, ripping Rodney's first pitch to the center field wall on one hop to plate pinch runner Peter Bourjos and Carpenter.

It was Piscotty's fifth game-winning RBI since being called up from Triple-A Memphis on July 21, giving him 30 RBIs in his first 45 major league games. As he stood on second, Piscotty pumped both fists to the dugout and yelled as the crowd of 43,557 exploded.

"I couldn't resist that time," Piscotty said. "The crowd was loud, it was exciting. It just came out of me."

It was the first lead of the series for St. Louis, which had been outscored by Chicago 20-6 to that point. Closer Trevor Rosenthal wasted little time wrapping it up, requiring just nine pitches to record his 43rd save.

The Cardinals (88-51) upped their division lead over second-place Pittsburgh to five games, pending the outcome of the Pirates' game in Cincinnati, and pushed the Cubs 7 1/2 games back.

Chicago (80-58) outhit St. Louis 11-5, touching starter Carlos Martinez for 10 hits and three runs in five innings. However, the Cubs stranded eight men during Martinez's stint, which wound up being crucial.

First baseman Anthony Rizzo and second baseman Tommy La Stella established a 2-0 first-inning lead for the Cubs with consecutive two-out RBI doubles. Center fielder Dexter Fowler grounded a run-scoring single an inning later to make it 3-1.

That was where the game stayed as Lester, who walked one and fanned seven, induced a variety of soft outs when he wasn't striking out the outmatched Cardinals.

"I felt good," Lester said. "My cutter felt better today. I got some mishits with that, which helped. I got away with a couple of pitches because of what we established earlier. Obviously, with the lineup they have, you're going to throw pitches. Every time, it seemed like I was in a 2-and-2 count."

So out came Lester, in came the bullpen and off went the Cardinals to a dramatic win that sent them off on a 10-game road trip in a good frame of mind.

"It was definitely good to get that one," Piscotty said. "You don't want to get swept by the Cubs. There was no panic in our ballclub."

Martinez walked one and fanned eight. The St. Louis bullpen permitted only one hit in four innings, with Jonathan Broxton (2-4) bagging the win after whiffing the side in the eighth.

NOTES: St. Louis 2B Kolten Wong (calf) didn't start for the third consecutive game. Wong experienced tightness before Monday's game and was a late scratch, then didn't play Tuesday night. ... Chicago gave 3B Kris Bryant, who played in 128 of the team's 129 games since his call-up from Triple-A Iowa, a day off. ... The Cardinals activated 1B Matt Adams (right quad) from the 60-day disabled list and designated LHP Nick Greenwood for assignment. Greenwood went 12-6 for Triple-A Memphis this year but lost in his only major league appearance of the season as a reliever.