The Brewers lamented their mistakes, especially after Ryan Braun hit a three-run home run in the bottom of the inning to make it a one-run game.
The Cubs celebrated their prized rookie, who isn't hitting homers, but continues to hustle.
"He's been struggling at the plate. Hits a routine ground ball to shortstop, beats it out, we score a run," Cubs manager Joe Maddon said. "How many guys do that?