SAN DIEGO — It was the middle of the game, but Matt Carpenter's ejection was the beginning of the end for St. Louis.
When San Diego's Ian Kennedy struck out Carpenter, which led to his ejection, and Stephen Piscotty with two runners on to end the fifth inning, it was preview of what was to come.
Kennedy escaped another tough jam in the seventh inning with the help of three relievers and Matt Kemp and Justin Upton keyed a seven-run bottom of the inning to lift the Padres to an 8-0 victory over the Cardinals on Saturday night.
Relievers Sean Kelley, Marc Rzepczynski and the recently acquired Bud Norris came in to strike out consecutive batters in the seventh with two men on to preserve a 1-0 lead.
San Diego then scored seven runs in the bottom of the inning, keyed by two-run hits from both Kemp and Upton. An error by third baseman Mark Reynolds led to three unearned runs.
"It was one of those innings that kind of blew up on us," Cardinals manager Mike Matheny said.
In the fifth, Tommy Pham had a one-out double and took third on pitcher Carlos Martinez's infield single. Kennedy struck out Carpenter and Piscotty to end the inning.
Carpenter was quickly ejected by home plate umpire Chris Segal for arguing after being called out on strikes.
"It was nowhere near the strike zone," Carpenter said. "It was an 0-2 pitch in a crucial point in the game and neither the pitcher nor the catcher wanted it anywhere near the plate.
"It was to set up their next pitch and he called it a strike. It was probably the worse strike I have ever had called against me."
The Padres escape was "the turning point in the game," according to Kelley. "We all basically had a guy to get out and we all did it. Then we came in and you saw how we responded. There was a lot of energy in the dugout, for sure."
The Cardinals (77-45) have the best record in baseball but have lost the first two games of the series by a combined score of 17-3.
The loss reduced St. Louis' lead in the NL Central to 3 1-2 games over Pittsburgh, which beat San Francisco 3-2.
The Padres, who have won nine of 11, tied their season high with their fifth straight win.
San Diego led 1-0 when the Cardinals threatened in the seventh against Kennedy (8-11).
Brandon Moss led off with a double and took third on Pham's single. Kelley replaced Kennedy and struck out Martinez, who had hits in his first two at-bats.
The left-handed Rzepczynski came in to strike out Kolten Wong and Norris struck out Piscotty looking.
Kevin Quackenbush and Odrisamer Despaigne each pitched a scoreless inning for San Diego's fourth shutout of the season.
Kennedy allowed seven hits, struck out 10 and walked one. Overall, Padres pitchers struck out 16 batters.
"It was not a good night offensively," Carpenter said.
"He took advantage of being able to spread the plate out," Matheny said. "It was smart pitching. He was very much on the corners. That's what he did and we couldn't do anything about it."
Martinez (12-6) lost his second straight start, allowing three runs and seven hits in 6 1-3 innings.
Travis Jankowski, who made his major league debut with the Padres on Friday night with two hits and an RBI, followed with two hits and two RBIs.
The Padres (61-62) have won four of six games against St. Louis to take the season series with just one game remaining. San Diego is the only National League team with a winning record against the Cardinals.
Cardinals: Although RF Jason Heyward started his second straight game, the team is being cautious about his sore hamstring.
Padres: C Derek Norris left the game with a bruised left hand in the eighth inning after Quackenbush struck out pinch-hitter Peter Bourjos. The strikeout pitch deflected off Norris' hand and bounced away, allowing Bourjos to take first. Norris went to his knees before coming out.
Cardinals: RHP Michael Wacha (14-4, 2.85 ERA) will look to increase his career highs in wins (14), starts (23), innings pitched (145 1-3) and strikeouts (125) in Sunday's series finale.
Padres: RHP Colin Rea (2-0, 4.22) will attempt to join Dave Freisleben (1974) as the only Padres to win their first three career starts. All three of Rea's starts have been at home.