"Sometimes you get lucky," he said. "That was lucky."
Westbrook worked around trouble almost the entire night in his second start since coming off the disabled list with a sore elbow. He gave up no earned runs, striking out two and walking three.
Edward Mujica pitched a perfect ninth inning for his 21st save in 21 attempts.
Westbrook said if he voted for MVP, his battery mate would certainly get the nod.
"With the way he's been hitting, but more importantly the way he's handled us as a staff and the way we've been pitching," Westbrook said. "He, in my mind, is the reason for that."
Molina is hitting .365 and is pulling away from the field. Colorado's Troy Tulowitzki, who is on the disabled list, is second at .347. Molina is just outside of the top 10 in RBIs (41). He's also helped the Cardinals pitching staff post the major league's second-best ERA (3.28).
Allen Craig reached in the fifth after second baseman's Darwin Barney's throw on the back end of a double-play attempt went to the Cardinals dugout. Molina drove a 1-2 pitch just over the outfield wall to improve to 9 of 15 with three homers against Jackson.
Jay went to third on a hit-and-run with Daniel Descalso singling to right and scored on a hit from Pete Kozma to give St. Louis a 4-1 lead.
Westbrook retired the Cubs in order in the first and seventh innings, allowing at least one runner to reach in the five innings between. He faced the minimum in three of those five innings. Two runners were erased on inning-ending double plays and Luis Valbuena was caught stealing on a pitchout for the first out of the third.
"He was good," Molina said of Westbrook. "That sinker was moving a lot."