Carpenter tripled on Kershaw's first pitch of the game but didn't budge when the lefty retired the next three on nine pitches.
The Cardinals had another runner at third with nobody out in the fifth after Freese doubled and advanced on a passed ball by Ellis, This time they converted on Jay's sacrifice fly to shallow left as Crawford's throw was well offline.
The previous pitch the Cardinals tried to squeeze in a run with the Dodgers infield playing in, but Jay fouled off a 1-1 pitch.
Kershaw worked six snappy innings, needing just 72 pitches. He gave up two hits and struck out five.
The majors' ERA leader had plenty left, too, but the Dodgers needed runs and manager Don Mattingly opted for pinch-hitter Michael Young after Nick Punto's two-out single in the seventh.
"I always want to stay in the game, but I understand where Donnie's coming from," Kershaw said. "I get it. We can't give up any more outs and Michael Young is one of the best players the last 10 years."
The Cardinals lifted Wacha for another stingy rookie. Siegrist, who had a minuscule 0.45 ERA in his debut season, threw a pair of wild pitches before getting Young on a flyout to end the seventh.
Relievers Randy Choate and Carlos Martinez pitched the eighth for St. Louis before turning it over to Rosenthal.
The Cardinals handed Kershaw two of his nine losses this season and have beaten him four consecutive times overall.
NOTES: SS Ramirez was a late scratch with sore ribs after getting plunked in the first inning of Game 1. Ethier has been slowed by a sore ankle. ... Carpenter has a hit each of the first two games after entering the NLCS in a 3 for 39 slump. ... Choate, the lone veteran reliever the Cardinals used in Game 2, has gotten two outs on four pitches in two appearances.