CHICAGO -- The difference between winning and losing was just a few feet on Friday.

Milwaukee's Ryan Braun clubbed a two-run first-inning home run -- the 300th of his career. Chicago's Anthony Rizzo saw a potential go-ahead home run in the fifth inning reach the center field warning track and go no further.

And in between was stingy pitching by both teams as the Brewers claimed a 2-0 victory over the Cubs to open a three-game Wrigley Field series.

Braun's two-run homer with one out in the first inning helped the Brewers (73-68) pick up a game on the first-place Cubs (77-64). Milwaukee now trails Chicago by four games.

"It's really a cool number, no question about it (with) just the longevity and consistency it takes to get there," Braun said of his 300-homer milestone. "But obviously with where we're at in the season, we're focused on bigger and more important things."

Chicago has now lost four of its last six games since a six-game winning streak.

Brewers right-handed starter Jimmy Nelson (12-6) earned his third straight victory in a five-inning outing, allowing just four hits while walking two and striking out seven. He abruptly left the game after five innings with right arm soreness.

Nelson took a longer view as he preached consistency.

"One game is not more important than the other," he said. "Every single game is important. We don't need to try to do anything more tomorrow than we did today."

Closer Corey Knebel, the last of four Brewers pitchers, gave up one hit in a scoreless ninth inning for his 33rd save.

Cubs right-hander John Lackey (11-11) took the loss despite giving up just two earned runs on four hits while striking out nine and walking two. He threw 105 pitches in his seven-inning outing.

"I felt really good tonight," Lackey said. "After a week off I was almost too strong in the first inning. I threw too many fastballs and was up in the zone a little bit. Once I got settled in things started rolling pretty good."

The game, witnessed by a crowd of 41,020, was the first Friday night game ever played at Wrigley Field during the regular season since lights were installed in 1988.

Braun's 15th homer of the season came on Lackey's 0-1 pitch. He deposited it over the center field fence while driving home Eric Thames.

Ben Zobrist doubled to lead off the Cubs' second and reached third on a wild pitch with one out. But Chicago came up empty as Ian Happ grounded out to the pitcher and Javier Baez flew out to center.

The Cubs threatened again in the third with two outs and Rizzo at first and Kris Bryant perched on third. But Nelson struck out Zobrist looking on a full count to end the inning.

Chicago had a third two-out threat in the fifth with runners at first and third and Rizzo at the plate. But the Cubs fell short again when Rizzo sent a deep fly to the center field warning track.

"Rizzo hit a three-run homer that stayed in the park, their guy (Braun) punctured the wind," said Cubs manager Joe Maddon. "I have nothing to complain about. It was a really good game of baseball. They won."

NOTES: Former Georgia football coach Vince Dooley threw out the first pitch to cheers from red-clad Bulldogs fans in town for Saturday's football game at nearby Notre Dame. ... Brewers LF Ryan Braun is now the 12th active player with 300-plus career home runs and is the franchise's all-time home run leader. ... The Brewers send RHP Chase Anderson (8-3, 3.06 ERA) against Cubs LHP Mike Montgomery (5-7, 3.38 ERA) in Saturday's middle game. .... Cubs C Willson Contreras continued his rehab work on Friday as designated hitter at Class A Myrtle Beach in the Pelicans' final game of the season. He's scheduled to return to Chicago on Saturday, but there's no firm date for reactivation by the Cubs. ... Of Chicago's 21 remaining games, 13 are against teams with records above .500 and eight are against clubs below .500. Sixteen of the final games are against Central Division foes.