KANSAS CITY, Mo. -- Third baseman Matt Carpenter and the St. Louis Cardinals made sure right-hander Michael Wacha got all the runs he would need and then some.

Carpenter belted a two-run homer and Wacha threw seven strong innings as the St. Louis Cardinals downed the Kansas City Royals 6-1 on Sunday to avoid being swept by their cross-state rivals.

Carpenter, who has a .436 batting average in 10 games at Kauffman Stadium, homered in the sixth with second baseman Kolten Wong aboard.

"The only really bad pitch (Yordano Ventura) made all day was when he pulled a change-up to Carpenter up and in," Royals manager Ned Yost said. "He hit it down the line. I didn't think there was any way to keep it fair, but that's what good hitters do."

Cardinals manager Mike Matheny noted Ventura made a couple of throws to first to pickoff Wong, who distracted the pitcher.

"Then Carpenter made a nice short stroke," Matheny said.

Wacha (7-0), a 2012 first-round draft pick who missed 68 games last season with a shoulder injury, stymied the Royals on five hits and one unearned run. The Cardinals are averaging more than six runs a game in his nine starts.

Catcher Yadier Molina hit a two-run single in the eighth to cap off the Cardinals scoring. The inning also included first baseman Matt Adams' second double.

Ventura (3-4) was replaced by Luke Hochevar to start the eighth after surrendering four runs on five hits and two walks, while striking out seven.

The first inning started poorly for Ventura. He walked leadoff batter Wong on four pitches. Ventura worked the count full on Carpenter before walking him, which prompted a mound visit from pitching coach Dave Eiland.

Ventura yielded a run-producing single to designated hitter Jhonny Peralta and an RBI double to Adams. At this juncture, Ventura had thrown 18 pitches without retiring a hitter and put the Royals in a 2-0 hole with Cardinals residing on second and third base eager to increase their lead.

Then a base-running blunder by Peralta aided Ventura. When a Ventura pitch in the dirt bounced a few feet away from catcher Salvador Perez, Peralta started to come home and was caught in a rundown for the first out.

"It's awesome when, before you step on the mound, you've got a 2-0 lead," Wacha said.

After Peralta's base-running gaffe, Ventura retired the next 14 batters, striking out five.

The Royals' offense, however, could do little with Wacha, who gave up two hits and walked one in the first four innings. Wacha coaxed Perez and first baseman Eric Hosmer to ground into double plays in the second and fourth innings.

"We had him on the ropes a couple of innings, but he made some good pitches to get out of those jams," Hosmer said. "That's why he's got the numbers he's got."

Center fielder Peter Bourjos' fifth-inning error gifted the Royals with an unearned run in the fifth. With one out, left fielder Alex Gordon's fly escaped Bourjos, and Gordon raced to second base. Perez brought him home with a single, extending his hitting streak to 10 games.

And that was all the Royals would get off Wacha and two relievers.

"Wacha's tough, man," Yost said. "He spots his fastball well. A lot of times you can rank pitchers pitches, fastball number one, curveball number two and change-up number three. All three of his pitches are good, effective pitches. It is hard to rate them, all three are so good."

NOTES: LF Matt Holliday, who has reached base in his first 40 games, was a game-time scratch from the Cardinals lineup with a contusion on his strained left forearm after being hit by an Edinson Volquez pitch Saturday night.. .. RF Alex Rios, who has missed 35 Royals games with a fractured left hand, will begin a minor league rehab assignment Monday with Triple-A Omaha. ... Royals RHP Jeremy Guthrie, who starts Monday at New York, is 3-0 o