DENVER - Before the Cardinals reach the stretch of games that will decide the division title and things really get rocky, they conclude their schedule against lackluster teams with a visit to Coors Field and a series against one of the National League's most disappointing clubs that can play as thin as its air.

But, it does have Nolan Arenado.

One of the best all-around players in the game, Arenado did Arenado things Tuesday night - launching moonshots, heisting singles - and led the Rockies to a breezy, 2-1 victory against the Cardinals in front of a partisan, red-clad crowd in Denver's lower downtown ballpark. Arenado's two-run homer in the first inning off Cardinals starter Michael Wacha proved the be all the runs the hosts would need as starter Chi Chi Gonzalez and a parade of relievers allowed the Cardinals to hint at rallies, but never make them.

Once they leave Colorado, the Cardinals begin a stretch of 16 games to conclude the regular season _ and all 16 will be against teams with a winning record. The race in the National League Central shifted dramatically Tuesday night for Milwaukee as reigning MVP Christian Yelich, a candidate to repeat as MVP this season, left the game with a fractured knee cap. The team announced that he would miss the remainder of the season. The Brewers will visit Busch Stadium this weekend to start the gauntlet that the Cardinals must survive to reach the playoffs for the first time since 2015.

Coming off his short-rest start that helped the Cardinals set their rotation for that run of contending teams, Wacha had his start abbreviated again Tuesday _ this time by strategy more than his performance. Wacha struck out three and allowed five hits through four innings. He left a change-up over the plate to Arenado with a runner on in the first inning, and Arenado drove it beyond the bleachers stationed past left field. The ball traveled an estimated 482 feet. The homer was Arenado's 38th of the season and the 500th extra-base hit of his career. He joins former Cardinal Larry Walker as one of four players in Colorado history with that many extra-base hits for the club.

One of the last spasms of unsuccessful offense came in the top of the eighth for the Cardinals - not with a swing or a walk, but with a slide that dodged a brilliant play by Arenado.

Rockies reliever Jairo Diaz had retired the first two batters of the inning when he faced birthday boy Paul Goldschmidt. The Cardinals' 32-year-old first baseman and longtime Rockies rival as an Arizona Diamondback hit a hard groundball down the third-base line. As familiar as anybody with Arenado's magic at the hot corner, Goldschmidt sprinted for first - and when Arenado's throw brought first baseman Daniel Murphy off the bag, Goldschmidt dropped into a feet-first slide that went outside of the base and past it. Along the way he limbo'd under Murphy's attempted tag to steal a single.

It proved fruitless when a strikeout ended the inning, with Goldschmidt still standing at first base. He was the sixth runner the Cardinals left on base in the game.

Three were left in scoring position.

Two stood at third.

The move for a pinch-hitter in the top of the fifth inning would have been more compelling, more urgent, more barstool debate-worthy had it happened in any of the summer months before September. But with both the bases and bullpen loaded, the choice to yank Wacha early from his start and go for the gusto of offense was obvious.

A fielding error at first and back-to-back singles from the bottom of the lineup brought Wacha's spot up with the bases loaded, two outs, and one run separating the Cardinals from the Rockies. With at least three long relievers, including Ryan Helsley, available in the bullpen and a total of a dozen relievers on the expanded roster, manager Mike Shildt sent Matt Carpenter to the plate and ended Wacha's start after four innings. The expanded rosters of September allowed him to take a chance with the bases loaded and plenty of arms to cover the innings in the night and days ahead. While so tantalizing at any point in the season, a move like that in July or August might leave a pitching staff exposed in another game during the series at Coors.

Carpenter, a .481 hitter with the bases loaded, flipped a line drive that fell shy of shallow center field and into the shortstop's glove for an out that broke the rally.

Dexter Fowler grounded out to end the inning.

The bases _ loaded with one out _ remained so at the third out.

It didn't take long for the Rockies' bullpen to escort the Cardinals to another chance to tie the game. Bryan Shaw walked the first batter he faced. He hit the second batter he faced.

The Rockies were again on the ledge, poised to slide.

They didn't.

Righthanded reliever Carlos Estevez entered and promptly struck out the two batters he was assigned. Each came to plate with the tying run at third base. Each didn't budge the tying run from third base. Estevez got pinch-hitter Jose Martinez on three pitches. The Cardinals slipped to one-for-eight with runners in scoring position, and the one hit was a single that just moved a runner to third, not brought a run home.

The Cardinals got a one-out single in the ninth, and the game ended with a double play, one confirmed by replay.