(Reuters) - The Milwaukee Brewers launched the National League baseball playoffs with a 4-1 victory over the Arizona Diamondbacks in Saturday's opening game of their best-of-five division series.

Prince Fielder, the burly, bearded slugger who led Milwaukee with 38 home runs this season, belted a two-run shot in the seventh inning to increase the Brewers' lead to 4-0 on their way to victory.

Yovani Gallardo, who was 17-10 in the regular season, registered the win by going eight innings and yielding one run on four hits, while striking out nine against just one walk.

Arizona's Ian Kennedy, who posted a sterling record of 21-4 this season, took the loss. Kennedy was knocked out in the seventh inning after giving up all four runs on eight hits.

Milwaukee took a 1-0 lead in the fourth inning on a sacrifice fly to center that scored Ryan Braun, who raced to third base on a double by Fielder.

The Brewers added another run in the sixth when catcher Jonathan Lucroy singled home Yuniesky Betancourt.

Arizona's lone run came on a home run by Ryan Roberts in the eighth.

The NL-best Philadelphia Phillies host the wild card St Louis Cardinals later Saturday in the opener of the league's other playoff series.

Zack Greinke (16-6) is scheduled to start for Milwaukee in Game Two of the series Sunday, while the visiting Diamondbacks counter with Daniel Hudson (16-12).

(Writing by Larry Fine in New York, Editing by Julian Linden)