Hart homers twice, Brewers beat Cardinals 6-0
Rickie Weeks homered while Aramis Ramirez and Carlos Gomez added RBI doubles for the Brewers, who rebounded after dropping Friday's opener. Ryan Braun had a pair of doubles and drew a walk after going 0 for 5 on Friday.
Greinke (1-0) continued the dominant form he showed at Miller Park all last season. He didn't walk a batter and struck out seven.
Greinke's strong outing overshadowed the long-awaited return to the mound for the Cardinals' Adam Wainwright, who missed all of the 2011 season after having elbow surgery.
Wainwright (0-1) went 5 2-3 innings, giving up four hits and three runs with a walk and six strikeouts. It was his first regular-season start since Sept. 24, 2010, a span of 563 days.
Hart led off the second with a monster home run, so deep that left fielder Matt Holliday didn't even move when the ball came off the bat.
Wainwright settled down until the sixth, when he allowed a leadoff single to Weeks, then committed a throwing error that allowed Nyjer Morgan to reach first on a sacrifice bunt attempt.
Wainwright then got Ryan Braun to hit into a double play, sending Weeks to third. Ramirez doubled off the wall in left-center field, scoring Weeks to give the Brewers a 2-0 lead.
Cardinals manager Mike Matheny lifted Wainwright in favor of Victor Marte, and Corey Hart pounced on a pitch for a two-run homer to center and a 4-0 lead. It was the 12th multi-homer game of Hart's career.
Greinke gave up only three hits in the first five innings: a pair of singles by David Freese, one of which was an infield hit, and a ball off the bat of Jon Jay that originally was ruled an error but later was changed to a base hit.
Things seemed to start unraveling in the sixth, when Greinke gave up a one-out single to Rafael Furcal and allowed him to go to second base on a wild pitch. But Greinke struck out Carlos Beltran and got Holliday to ground out.
Greinke was unbeatable at home for the Brewers last season, going 11-0 with a 3.13 ERA in 15 home starts during the regular season, and getting a win in the playoffs.
Greinke can become a free agent at the end of the season, making his future a critical question for the Brewers. General manager Doug Melvin said Friday that he and Greinke's agent, Casey Close, discussed a potential new deal.
Francisco Rodriguez pitched a scoreless eighth and Jose Veras closed out the ninth for Milwaukee.
NOTES: Brewers broadcaster Bob Uecker was back on the air Saturday, one day after the death of his son, Steve. ... Weeks originally was charged with an error in the fifth when a ball hit by Jay glanced off his glove. The play later was changed to a base hit. ... Wainwright threw 88 pitches, 66 of them for strikes.