Wainwright remained unbeaten in the postseason, going to 3-0 with a 2.27 ERA in 14 games, five of them starts.
He allowed a run on three hits in seven innings, striking out nine without a walk. The only damage came on a homer by Pedro Alvarez to start the fifth.
The right-hander tied for the NL lead with 19 wins this year and was 4-0 in his past five starts. He thrives on expectations.
“I’d love to be that guy,” Wainwright said. “It’s important to have somebody go out there that you can count on for sure.”
Wainwright also started the Cardinals’ big burst with a leadoff, full-count walk.
Beltran, who has never reached the World Series, reprised his role as one of the game’s greatest playoff sluggers. His 443-foot drive to the distant second deck in right field put St. Louis ahead and was the second-longest shot by a left-handed batter at 8-year-old Busch Stadium.
“I almost got caught up in the moment,” said Wainwright, who had a perfect view from second base. “I threw my hands up in the air as soon as he hit it, I knew it was gone.
“Then I realized I had to run.”
Beltran has 15 home runs, 10 doubles and 28 RBIs in 35 postseason games. He also has scored 40 runs and stolen 11 bases.
Leadoff man Matt Carpenter called Beltran “Mr. October.”
“He’s like our secret weapon when it comes to the postseason. He steps up every time,” Carpenter said. “Some guys just have a knack for a big game and he’s one of them.”
Beltran’s 13 career RBIs against Burnett are the most of any player.
Beltran’s homer got the Cardinals going, and Jon Jay later walked with the bases loaded. Freese added a two-run single that cleared the bases when right fielder Marlon Byrd’s throw to the plate deflected off Freese’s leg for an error.