With the Dodgers in danger of falling 3-0 behind in the best-of-seven series, South Korean Ryu stood up to the Game Three pressure and tossed seven scoreless innings as Los Angeles trimmed the deficit to 2-1.
"It gets us on the board, that's the main thing. We grab a little momentum on our side," Dodgers manager Don Mattingly said.
"(Ryu) has pitched big in a lot of big games this year. The experience of the (National League Division Series) really helped him today."
The Dodgers broke through with two runs in the fourth to snap a stretch of 22 scoreless innings and Hanley Ramirez returned to the line-up from a rib injury with two hits and an eighth-inning RBI.
In the fourth, Adrian Gonzalez brought the Dodger Stadium crowd to its feet with an RBI double and Yasiel Puig followed with a run-scoring triple.
Puig's hit was his first of the series, ending an 0-for-11 slump, and the blast was just a fraction short of clearing the fence for a home run.
The 22-year-old Cuban outfielder initially raised his arms thinking it was a round-tripper but still managed to reach third after seeing it fall short with a display of arrogance that seemed to rub the Cardinals the wrong way.
In all, Los Angeles got two hits apiece from Puig, Ramirez and Mark Ellis, which was more than enough for Ryu, who allowed just three hits, before Brian Wilson worked the eighth and Kenley Jansen nailed down the ninth.
St Louis ace Wainwright, who had won his two prior starts during these playoffs, pitched seven innings in the defeat.
The Cardinals were hurt by defensive and base-running miscues, including a fly ball in the fourth that fooled outfielders Carlos Beltran and Jon Jay as it led to a double.
"That was not characteristic of how we've played all season," Cardinals manager Mike Matheny said.
"We had a lot of balls in the air tonight that hit the ground that normally don't. We're a better club than this."
On the winning side, Ramirez, who sat out of Game Two on Sunday after being hit with a pitch in the series opener and sustaining a cracked rib, pushed through the pain barrier to spark the Dodgers.
"I got here early, got treatment and the guys took care of me," Ramirez said. "I'm happy we got the first win. We'll come back and try to even up the series."
Game Four is in Los Angeles on Tuesday.
- Sports & Recreation
- Hanley Ramirez
- Los Angeles
- Yasiel Puig