DENVER -- German Marquez was impressive in his first major league start and Nolan Arenado hit a grand slam as the Colorado Rockies piled on rookie starter Luke Weaver early and beat the St. Louis Cardinals 11-1 on Wednesday.

The victory enabled the Rockies to avoid being swept in the three-game series and ended the Cardinals' four-game winning streak. St. Louis slipped a half-game behind the New York Mets and San Francisco Giants in the National League wild-card race, pending their games on Wednesday night.

Arenado's grand slam came with two outs in the second and was his first since Sept. 26, 2015, against the Los Angeles Dodgers and the fourth of his career. It was his National League-leading 39th homer and gave the Rockies a 6-1 lead. Arenado drove Weaver's first pitch an estimated 424 feet to left-center.

"It was just a fastball in," Weaver said. "A lot of the fastballs were moving. I definitely needed that two seam to move in, and it's the only fastball I think that stayed straight. To me, it's very frustrating because I'm trying to throw a pitch to get in there, and for it to flatten out at such a big moment right there is disappointing."

Marquez (1-0) became the second-youngest Rockies pitcher to earn a win at 21 years, 212 days. Jamey Wright was 21 years, 206 days when he won his first game in 1996.

Marquez gave up one run and four hits in five innings with one walk and three strikeouts. He had made three relief appearances since being recalled by the Rockies earlier this month, throwing a combined 52 pitches in three innings in his past two games.

Since Marquez had not started since Sept. 3 with Triple-A Albuquerque, he was going to be limited to around 80 pitches and left after throwing 82 pitches.

"He was really impressive," Rockies manager Walt Weiss said. "It's easy, easy velocity. Very effortless. He commanded the ball, showed a very good curveball. Great poise."

Marquez did more than simply command his 94-95 fastball.

"He's clipping corners with that thing," Weiss said. "When you're doing that at that velocity, it's tough to handle. He had it all working."

The Rockies acquired Marquez and reliever Jake McGee in a January deal that sent outfielder Corey Dickerson and a minor league infielder to the Rays.

Marquez, who spent most of the season at Double-A Hartford and was named the Eastern League Pitcher of the Year, is scheduled to make two more starts -- Tuesday at San Francisco and Oct. 2 against Milwaukee in the final game of the regular season.

Marquez hit two batters but faced only four batters with a runner in scoring position and yielded nothing more damaging than Kolten Wong's sacrifice fly that tied the game at 1 in the second after DJ LeMahieu's sacrifice fly brought home Charlie Blackmon in the first.

Jordan Patterson, making his first major league start, began the second with a single, his first major league hit. Daniel Descalso followed with a single that sent Patterson to third.

Marquez put down a good bunt toward first base on a sacrifice attempt, but Weaver scooped up the ball and threw Patterson out at home.

Blackmon singled home a run and, after Carlos Gonzalez walked to load the bases, Arenado, who had four hits in his past 21 at-bats when he belted his grand slam that increased his major league leading RBI total to 128.

"These day games are tough to get going for, especially this time of year when your body is kind of sore and stuff," Arenado said. "I just tried to take a nice swing and not get big. I was able to hit it hard."

Chris Rusin followed Marquez with five strikeouts in two scoreless innings, giving Rusin seven straight scoreless appearances totaling seven innings -- with no walks and 13 strikeouts in that stretch.

The Rockies blew the game open with a five-run seventh, highlighted by Tom Murphy's three-run homer. It was his fifth homer since being added to the roster earlier this month.

During the rally, LeMahieu doubled home a run. He went 2-for-3 to extend his career-high on-base streak to 37 consecutive games and raise his National League-leading average to .351, the highest it has been since April 15. He's four points ahead of Washington's Daniel Murphy with the Nationals playing Wednesday night.

NOTES: Rockies third base coach Stu Cole was sidelined a second day on doctor's orders but will return Thursday. He was hit in the head with a ball while he was throwing batting practice Tuesday. ... Cardinals LF Matt Holliday (fractured right thumb) will take live batting practice Friday at Wrigley Field. He reported minor swelling in his thumb after hitting in the indoor cage at Coors Field two straight days. ... St. Louis C Carson Kelly made his second major league start and eighth career appearance. With the Cardinals idle on Thursday, C Yadier Molina will get two days off.