PHOENIX -- The Brewers held on to their big lead this time.
"I think that's the key for us," Fielder said. "When we score early it helps the whole team."
Fielder drove in four runs and Bill Hall hit a three-run drive for the Brewers, who won for the second time in eight games to pull even with the Cubs in the division.
Milwaukee led 5-0 against Cincinnati on Sunday and lost 7-6. But there were no such issues against the Diamondbacks thanks to rookie Yovani Gallardo, who struck out six in six innings and hit his first major league homer.
"The past couple of starts have been a little bit rough so it's always good to get back in the groove," Gallardo said.
Reserve infielder Jeff Cirillo pitched a scoreless ninth for the NL West-leading Diamondbacks, who lost consecutive games for just the third time since the All-Star break. Cirillo walked two and struck out one.
Cirillo is the second Arizona position player to pitch in less than a week. Augie Ojeda pitched a scoreless inning in the Diamondbacks' 14-5 loss to Florida last Tuesday.
Arizona's division lead over idle San Diego dropped to 3½ games. The Diamondbacks have lost six games by nine or more runs this season.
"We've played a few of these this year so what are you going to do," Arizona manager Bob Melvin said.
Gallardo (5-3) allowed five hits and walked one to snap a personal two-game losing streak.
"He wasn't super sharp but he was good enough to get through six shutout innings," Brewers manager Ned Yost said.
Carlos Villanueva pitched three innings to complete the five-hitter and earn his first major league save. He was optioned to Triple-A Nashville after the game when Milwaukee promoted reliever Seth McClung.
"I wanted to do it last night but McClung couldn't pitch today and we needed the pitching," Yost said.
The Brewers wasted little time scoring against Arizona starter Doug Davis (10-11).
Milwaukee added three more in the second when Gallardo hit a one-out homer and Fielder added a towering two-run, two-out shot to right. Fielder leads the NL with 39 homers.
Davis went just two innings, a season low, and allowed six runs and six hits with two walks and one strikeout. He lost a personal five-game winning streak.
"The control wasn't there," Davis said. "I got behind hitters and I just made some real bad pitches tonight. I got behind every hitter and it seems like when I did get ahead I made a mistake and put it right over the middle for them."
Fielder added a three-run double off Edgar Gonzalez in the fourth to make it 9-0.
- Yost said Villanueva will make two starts with Nashville and likely return after rosters expand next month.
- When Cirillo came in, catcher Chris Snyder went to third, Mark Reynolds moved from third to second and Conor Jackson moved from first to third.
- The Diamondbacks have been outscored 69-16 in their last seven losses, dating to July 29.
- Brewers RF Corey Hart was a late scratch with a sore right elbow. He was replaced by Joe Dillon.
- Twenty-four of Fielder's 39 homers have been solo shots.
- Davis had allowed five homers in 151 2-3 innings entering Monday's game.
- Diamondbacks RHP Micah Owings, who homered twice and had six RBI Saturday night in Atlanta, pinch-hit for Davis in the second and walked.
- Snyder's first-inning error was his first since September 5, 2006, a span of 92 games.