PITTSBURGH -- Jordy Mercer was at the center of the biggest moment of the game and had a front-row seat for the oddest.

Mercer's three-run double in the sixth inning rallied the Pittsburgh Pirates to a 7-5 victory over the St. Louis Cardinals on Saturday night.

While the shortstop's hit lifted the Pirates (14-15) to their second win in three games since a five-game losing streak, it was almost a footnote to Pittsburgh turning the first 4-5-4 triple play in major league history in the second inning.

In the top of the second inning, with the game scoreless, the Cardinals had shortstop Jhonny Peralta on third base and right fielder Jason Heyward on second with no outs when catcher Yadier Molina lined out to second baseman Neil Walker.

Walker threw to rookie third baseman Jung Ho Kang to double Peralta off third base. Kang initially started walking toward the Pirates' dugout, thinking the third out had been made, but he threw back to Walker to double Heyward off second base for the third out.

"That was crazy," said Mercer, who watched it all unfold right in front of him. "You never expect something like to happen."

Neither did Kang, the rookie from South Korea.

"That was fun to watch, but I'm not so sure where Kang was at the end," Pirates manager Clint Hurdle said. "I was just hoping he didn't throw the ball in the stands. We got his attention in time to finish it off. Everybody, in multiple languages."

The Pirates also turned a triple play on Sept. 14 against the Chicago Cubs.

The Cardinals last hit into a triple play on May 10, 2003, with Atlanta Braves shortstop Rafael Furcal turning it unassisted after catching a liner by pitcher Woody Williams with runners on first and second.

Current St. Louis manager Mike Matheny was the runner at second base.

While the triple play abruptly ended a Cardinals rally, they lost the game in the sixth inning when sinkerballing right-hander Seth Maness came on to relieve Carlos Martinez (3-1) with a 5-4 lead, one out and the bases loaded.

Mercer hit a drive off the fence in front of the bullpen in center field. A single by left fielder Sean Rodriguez and walks to first baseman Pedro Alvarez and catcher Francisco Cervelli filled the bases.

Mercer, hitting just .191 in 29 games, stood on top of second base and clapped his hand in an exaggerated fashion.

"I was just thinking: Be aggressive," Mercer said. "Look for something up, out over the plate and get it in the air. It's good personally; but, for the team, it's even better. We showed a lot of character."

The Cardinals' bullpen had won its previous six decisions.

"Seth and some other guys have been worked real hard and just couldn't get it that time," Matheny said. "He's made so many good pitches in situations like that; he's been so good getting us out of a jam. We needed a double play, couldn't risk another walk right there, and Seth's our guy."

Walker hit a solo homer to right field in the bottom of the fifth to draw Pittsburgh within 5-4.

Kang had two hits for the Pirates (14-16).

Right-handed reliever Rob Scahill (1-2) pitched a perfect sixth inning for the win. Closer Mark Melancon worked a 1-2-3 ninth for his sixth save.

The Cardinals (22-8), who have the best record in the major leagues, lost for the just the second time in 12 games.

Left fielder Matt Holliday had three of the Cardinals' 10 hits while Heyward doubled twice and Peralta had two hits.

Both starting pitchers struggled. The Pirates' Vance Worley gave up five runs and nine hits in five innings while Martinez was tagged for seven runs and seven hits in 5 1/3 innings.

Molina, two innings after lining into the triple play, hit a two-run double to key a five-run fourth that put the Cardinals ahead 5-3. Peralta drove in a run with a single, Heyward hit an RBI double and center fielder Jon Jay lofted a sacrifice fly.

The Pirates scored three runs in the bottom of the second to break a scoreless tie. Alvarez scored on a wild pitch and Mercer drove in a run with a groundout before Worley and right fielder Gregory Polanco hit back-to-back doubles for the third run.

NOTES: Cardinals 1B/3B Mark Reynolds started at third base in place of 3B Matt Carpenter, who is missing the three-game series with what the team is calling "extreme fatigue." ... Pirates INF Jung Ho Kang started at third base as 3B Josh Harrison, whose batting average has slipped to .178, sat out for the second time in five games. ... St. Louis LHP Tyler Lyons (0-0, 6.23 ERA) will oppose Pittsburgh LHP Jeff Locke (2-2, 4.85) on Sunday in the series finale.