ST. LOUIS -- On the brink of possibly being blown out in the top of the fifth inning, the St. Louis Cardinals instead assumed the lead before the inning was over, then did what the home team does so often in their contests with the Pittsburgh Pirates.

Rallying for three runs in the bottom of the fifth after denying Pittsburgh a prime scoring threat, St. Louis notched a 4-3 win Tuesday night in the opener of a series between the teams with the top records in the National League.

In upping their Central Division lead over the Pirates (65-45) to six games, the Cardinals (72-40) got three hits and the tie-breaking RBI from rookie left fielder Stephen Piscotty and eight gutty innings from starter Carlos Martinez (12-4).

Both played prominent roles in the pivotal inning.

Martinez wriggled out of a first-and-second, no-out jam in Pittsburgh's fifth, inducing a 6-3 double play from center fielder Andrew McCutchen and a lineout from third baseman Aramis Ramirez that shifted momentum.

"That was huge," St. Louis second baseman Kolten Wong said of Martinez's escape act. "We knew we had to get something going on offense."

The Cardinals did, with help from Pirates starter Jeff Locke (6-7). Struggling with fastball accuracy throughout his five innings, Locke walked Wong and shortstop Jhonny Peralta to start the inning.

Right fielder Jason Heyward's groundball single to right scored Wong to make it 3-2. After an infield out moved two runners into scoring position, catcher Yadier Molina lofted a sacrifice fly that plated Peralta.

Piscotty then delivered the game-deciding knock, lacing a two-strike single to center that chased Heyward home.

"It's odd to see a rookie with the kind of disposition that Stephen has," St. Louis manager Mike Matheny said. "He's going about it the right way. He's using all the tools at his disposal -- doing his film work, talking with the other hitters -- and he's adjusted quickly."

Given his first lead of the night, Martinez kept Pittsburgh at bay, mixing in more off-speed pitches to complement a fastball which was still touching 96 mph during the eighth inning. Martinez permitted nine hits and three runs, walking none and fanning eight.

"I know they've seen me before," he said through an interpreter, "so they know I throw hard. I had to throw other pitches to keep them off-balance."

Closer Trevor Rosenthal, who blew consecutive save chances just before the All-Star break in extra-inning losses to the Pirates, fanned the side in the ninth for his 34th save.

Pittsburgh nicked Martinez for runs in three of the first four innings. Shortstop Jung Ho Kang delivered a two-out RBI double in the first, while Ramirez snapped a 1-1 tie in the third with a two-out run-scoring single.

First baseman Pedro Alvarez upped the lead to 3-1 an inning later, rifling a first-pitch bolt 446 feet over the wall in center for his 16th homer of the year.

But that was it for the Pirate attack as they fell to 0-4 in Busch Stadium, continuing a recent trend of the home team dominating this matchup. Home teams are 9-2 in the series this year, with seven games decided by one run.

"It doesn't matter how you lose," McCutchen said. "No one likes to lose. All you can do is get ready for tomorrow."

Locke yielded seven hits and four runs over five innings, issuing three walks and striking out three.

NOTES: Pittsburgh 3B Josh Harrison (left thumb) and SS Jordy Mercer (left knee) started rehab assignments Tuesday at Triple-A Indianapolis. Harrison has been out since July 6 and Mercer went on the 15-day DL two weeks later. ... St. Louis 3B Matt Carpenter entered Tuesday night's game with extra-base hits in six straight games, giving him 16 since the All-Star break. Only Colorado RF Carlos Gonzalez has more in the National League with 17. ... Pirates RHP Vance Worley has accepted his assignment to Indianapolis. Worley was designated for assignment July 30 after the team traded for RHP Joe Blanton.