It was the first four-homer opening day in the history of the Cardinals.
Pujols, winner of the National League MVP award each of the last two seasons, went 4-for-5. He hit a solo homer in the first and added a two-run blast in the seventh.
The Cardinals had a two-run lead before producing five runs in the ninth -- four of them coming on Molina's blast.
Chris Carpenter claimed the victory, giving up two runs on five hits with three strikeouts in six innings.
Joey Votto and Scott Rolen hit homers for Cincinnati in the fourth.
The loss went to Aaron Harang, who gave up four runs on five hits in five innings. He equaled a franchise record with his fifth consecutive opening day start.
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