Skip Schumaker hit his first career grand slam during St. Louis Cardinals' biggest inning of the season, supplying more than enough runs for right-hander Chris Carpenter to beat the Cincinnati Reds for the ninth time in a row, 7-3 on Monday night.

The Cardinals provided a lopsided start to their showdown for first place in the NL Central, trimming Cincinnati's lead to one game.

St. Louis sent 12 batters to the plate for seven runs in the fourth, giving rookie Mike Leake (7-4) his worst moments in the majors. Schumaker's grand slam — only his 19th career homer — made it 6-0.

Carpenter (13-3) has won his last nine starts against the Reds, a streak that started in 2006. He gave up five hits and a pair of runs in seven innings.

Ramon Hernandez had three of Cincinnati's seven hits, including an RBI double off Carpenter and a solo homer off Kyle McClellan.

The crowd of 36,353 was revved for one of the most meaningful series in Great American Ball Park's eight-year history. The Reds haven't been in first place so late in a season since 1999, when they were playing at Cinergy Field.

The Cardinals left the fans silently sweating in their seats.

The teams have been locked in a back-and-forth race since mid-May, never separated by more than three games since then. St. Louis leads the season series 8-5. They meet only one more time, for a three-game series in St. Louis from Sept. 3-5.

St. Louis has its top three pitchers set to start against the Reds during their showdown series — Carpenter, Jaime Garcia and Adam Wainwright. The Reds opened with a rookie.

For one of the few times, Leake looked like one.

St. Louis opened the fourth with six consecutive hits. The clincher came from Schumaker, who hadn't played since Wednesday because of a sore left wrist. His grand slam landed next to the Reds' bullpen in center and got Leake uncharacteristically flummoxed.

Leake even lost track of outs. He fanned Brendan Ryan for the second out in the fourth, then started jogging off the field. He realized his mistake just before reaching the foul line, turned around and gave up a single by Felipe Lopez. Manager Dusty Baker decided that was enough.

In his last two starts, Leake has given up 14 runs (six earned) and 15 hits in 8 2-3 innings. He sat in the dugout with sweaty hair stuck to the side of his forehand and a faraway expression in his eyes.

Carpenter had his way with the big lead, extending his streak of dominating an offense that leads the NL in batting, runs and hits. The right-hander beat the Reds four times last season, and now has beaten them four times already this season.

The Reds brought in another ex-Cardinal before the game, adding outfielder Jim Edmonds through a trade with Milwaukee. Edmonds played for Reds general manager Walt Jocketty in St. Louis. Edmonds started in center and went 0 for 4 with a strikeout.

NOTES: Carpenter is 4-0 in six starts since the All-Star break with a 1.79 ERA. ... Albert Pujols extended his hitting streak to nine games. He also walked for the first time in 12 games. ... Reds RHP Aaron Harang plans to throw a simulate game on Tuesday, then start a rehab assignment in the minors. Harang has been in the disabled list since July 6 with lower back spasms. ... The Reds optioned LHP Travis Wood to Triple-A to create a spot for Edmonds. Wood was going to miss his turn in the rotation because of two days off in the next week.