Yadier Molina and Matt Holliday had three hits each for St. Louis, which burst to a 3-0 lead in the second when Molina doubled in a run and third baseman Jerry Hairston Jr. allowed Garcia’s grounder to go through his legs. Holliday capped the scoring with a two-run single in the eighth.
Milwaukee’s infield nearly had a cycle of errors, with second baseman Rickie Weeks and shortstop Yuniesky Betancourt also committing miscues along with reliever Marco Estrada. Weeks had committed the Brewers’ only two errors in the first four games of the series.
St. Louis can wrap up the best-of-seven series and its 18th NL pennant on Sunday in Milwaukee. Edwin Jackson goes for the Cardinals against Shaun Marcum in a rematch of pitchers from Game 2, won by St. Louis 12-3 as neither starter received a decision.
The NL winner hosts the World Series opener against Detroit or Texas on Wednesday.
Milwaukee had not made more than three errors in a game during the regular season.