Staked to a 5-0 lead in the second inning, Ryan Dempster could not make it stand, allowing five runs and six hits in five innings with four walks and two strikeouts. Since being acquired from Florida on July 11, Dempster is 2-5 with a 7.39 ERA in 11 starts, with Cincinnati winning just three of those games.
Without a grand slam in his six previous seasons in the majors, Renteria blasted his second of the year in the bottom of the third inning to pull the Cardinals within 5-4. The shortstop added an RBI groundout in the eighth while Tino Martinez and Scott Rolen belted solo homers for St. Louis, which won for the fifth time in the last seven games.
Pujols had a double and three singles while Luther Hackman (5-4) tossed two scoreless innings in relief of Jamey Wright, who yielded five runs and six hits in three innings. Wright, who remained winless in five career starts at Busch Stadium, walked four and struck out one in his second start for the Cardinals since being acquired from Milwaukee on Thursday.
Lefthander Bruce Chen (2-5) took the loss, surrendering Rolen's first career homer as a pinch hitter in the sixth.
The victory was the 1,905th of Tony La Russa's career, moving him into an eighth-place tie with Casey Stengel on the all-time list.