ST. LOUIS -- Harrison Bader believed there was no reason to be nervous just because he was making his major league debut Tuesday night.

"You see the ball and hit it," the St. Louis Cardinals' new outfielder said. "There's no time to be anxious."

Heeding his advice when it most mattered, Bader started the game-winning rally with his first big league hit and ended it with a mad dash home on Jedd Gyorko's shallow sacrifice fly to right field in the ninth inning as St. Louis walked off the Colorado Rockies, 3-2.

The Cardinals (49-51) left their opponent on the field for just the third time this year. For that, they can thank Bader, whose contract was purchased earlier in the day from Triple-A Memphis after center fielder Dexter Fowler hit the 10-day disabled left with a left wrist strain.

Bader led off the ninth with a double into the left field corner off Jake McGee (0-1). Greg Garcia bunted Bader to third on the first pitch, and Gyorko pinch-hit for reliever Trevor Rosenthal.

With Colorado (58-44) using a five-man infield -- left fielder Gerardo Parra played first while Mark Reynolds moved from first into the middle of the diamond -- Gyorko lofted a 1-2 pitch from McGee to right fielder Carlos Gonzalez.

Third base coach Mike Shildt bet that Bader's speed would beat Gonzalez's arm. Gonzalez unleashed a good one-hop throw home that might have beaten Bader, but catcher Ryan Hanigan couldn't corral the short hop and Bader slid home safely as the remainder of a crowd of 41,514 erupted.

"That was a gamble on their part, but the gamble was speed, and it worked," Rockies manager Bud Black said.

Manager Mike Matheny said Shildt had to take a chance, noting that Bader nearly beat out a routine grounder to shortstop Trevor Story earlier in the game.

"You had to trust his speed," Matheny said. "I knew he was fast, but watching him get down the line in his first at-bat, that was impressive. You have to love that style of play."

Bader's legs made a winner of Rosenthal (3-4), who pitched a season-high two innings. Rosenthal worked out of a two-on, two-out jam in the top of the ninth, slipping a called third strike by Story.

It was Story who set up the dramatic ninth, golfing a good 1-2 sinker from Matt Bowman 405 feet into the Rockies' bullpen in left-center to start the eighth inning. The homer was Story's 14th of the year.

That long ball denied St. Louis starter Lance Lynn a victory despite another excellent start. Lynn worked six-plus innings, allowing only three hits and a run with two walks and six strikeouts.

In his past four starts, Lynn has yielded just two runs in 25 1/3 innings. The subject of trade rumors, Lynn was asked if he thought this might have been his last outing in Busch Stadium.

"We're four games back," he said, referring to how far they are out of first place in the National League Central. "I'm not going anywhere."

Colorado starter Jon Gray gave up eight hits and two runs in five innings, walking none and whiffing six in a 96-pitch effort. After ceding Paul DeJong's 13th homer, a two-run blast to the left-center-field seats in the first, Gray worked in and out of trouble for the outing's remainder.

It appeared the inability to add on to their early lead would catch up to the Cardinals when the Rockies' offense came alive late. Gerardo Parra's sacrifice fly in the seventh made it 2-1, and Story tied it an inning later.

However, Rosenthal kept the game even. That enabled Bader, the sixth player to make his big league debut for St. Louis this year, to take special memories from his first night in the majors.

"It's been a whirlwind in a sense, but I've been anticipating this for a while," Bader said.

NOTES: Colorado pitching coach Steve Foster was back with the team Tuesday, a day after leaving an 8-2 loss to St. Louis to check into a hospital after experiencing chest pains. ... The Cardinals placed RHP Adam Wainwright (mid-back tightness) on the 10-day disabled list Tuesday after his bullpen session. They haven't decided who will take his turn in the rotation Thursday night against Arizona. ... The Rockies recalled RHP Carlos Estevez from Triple-A Albuquerque and optioned RHP Jairo Diaz to Triple-A. It is Estevez's fifth stint with Colorado this year.