Wacha bested John Lackey in a matchup of present and past rookie sensations, Beltran provided a big hit and this time it was the Red Sox who were tripped up by fielding failures.
"Somebody would have to kill me in order for me to get out of the lineup," said Beltran, undeterred by bruised ribs that landed him in the hospital a night earlier.
Matt Holliday tripled and scored on Yadier Molina's fourth-inning grounder, but David Ortiz put Boston ahead 2-1 in the sixth when he pounced on an 85 mph changeup for a two-run homer just over the Green Monster in left field.
That ended Wacha's scoreless streak at 18 2-3 innings a rookie record for a single postseason but it was all he gave up. Selected by St. Louis last year with the first-round draft pick received as compensation when Albert Pujols signed with the Los Angeles Angels, Wacha has been so good lately that a St. Louis restaurant he walked into had named a milkshake after him, the "Wacha Wacha."
Wacha, the NL championship series MVP after beating Dodgers ace Clayton Kershaw twice, threw a career-high 114 pitches and allowed two runs, three hits and four walks in six innings with six strikeouts. He improved to 4-0 with a 1.00 ERA in four outings this postseason, matching the amount of regular-season wins he has in his brief career.
"They don't swing at bad pitches, really," Wacha said. "They did a good job tonight grinding out at-bats with me and got the pitch count up."
But then Lackey, who in 2002 with the Angels became the first rookie in 93 years to win a World Series seventh game, faltered in a three-run seventh. St. Louis went ahead when Matt Carpenter hit a sacrifice fly that led to a pair of runs, with the second scoring on errors by catcher Jarrod Saltalamacchia and reliever Craig Breslow both making their Series debuts.
Beltran, an eight-time All-Star, followed with an RBI single. He had been sent to a hospital for scans Wednesday night after bruising ribs while banging into the right-field fence to rob Ortiz of a grand slam. Beltran appeared to be wearing protective padding under his jersey.
"When I left the ballpark yesterday, I had very little hope that I was going to be in the lineup with the way I felt," he said. "When I woke up, I woke up feeling a little better. And I came to the ballpark, talked to the trainer. I was able to get treatment and talk to the doctors, and find a way to try anything I could try just to go out there and feel no pain."
He said he took an injection of Toradol to block the pain for five or six hours.
"The good thing is tomorrow I have the day off," he said.
When the Series resumes Saturday night in St. Louis, Jake Peavy starts for the Red Sox and Joe Kelly for the Cardinals. Twenty-nine of the previous 55 teams that won Game 2 to tie the Series went on to take the title.
"Excited to get home. I know everybody is," Cardinals manager Mike Matheny said.
St. Louis' hard-throwing bullpen combined for one-hit relief. Carlos Martinez got six outs, retiring Mike Napoli on an inning-ending popup with two on in the eighth. Trevor Rosenthal struck out the side on 11 pitches in the ninth for a save, whiffing Daniel Nava with a 99 mph fastball to end it.
Seeking its second championship in three seasons, St. Louis improved to 7-0 this postseason when scoring first and stopped Boston's World Series winning streak at nine. That run began with a sweep of the Cardinals in 2004, when St. Louis never led the entire Series.
This year's opener was more of the same, when the Cardinals made three errors and the Red Sox romped 8-1.
Lackey, pitching a day after his 35th birthday, returned this year after missing all of 2012 due to elbow surgery. In his first Series appearance since his Game 7 win 11 years earlier, he couldn't hold the lead Ortiz gave him with his 17th postseason homer, his fifth this year.
"We've got to go out there and play better than we did tonight," Ortiz said. "Nobody can dictate that you're going to win four straight games every time you go out there for the World Series."
NOTES: The Red Sox had not lost in the Series since Game 7 in 1986 against the New York Mets. ... With no DH allowed in the NL ballpark, Boston manager John Farrell said Ortiz will likely play first base in Game 3. Napoli would sit. ... Victims of the Boston Marathon bombings were honored during the seventh-inning stretch as singer James Taylor led the crowd in "America the Beautiful."