Davis (10-11) entered the game unbeaten in seven games since the All-Star break, sporting a 5-0 record with a 3.13 ERA and quality starts in seven of his last eight outings.
He would last just two innings in this one, surrendering three homers before exiting for a pinch-hitter in the bottom of the second with his team in a 6-0 hole.
"My control sure wasn't there," said Davis. "I got behind every hitter, I had to come to them and I just made some real bad pitches tonight."
In his first start against the Brewers, a team he spent the previous three seasons with, he issued five walks in six innings but gave up just two runs in getting a no-decision in a game the D-backs eventually won on July 18.
This time the free passes came back to bite him early. Davis entered the game with the third-most walks in the Major Leagues, and two first-inning free passes set up a Bill Hall three-run homer.
Brewers rookie starter Yovani Gallardo looked like Micah Owings in hitting his first Major League homer with one out in the second, as Davis tried to go down and in but left it out over the plate for Gallardo to pull down the line. After Milwaukee tacked on another run, Prince Fielder hit his 39th homer of the season before Davis was able to get out of the inning.
"It was just one of those days where I couldn't hit my spots -- I didn't do my job, bottom line," said Davis.
The Brewers lead the Major Leagues in homers and highest percentage of runs scored via the long ball.
The D-backs had their own chances to keep the game close early but were unable to get the big hit off of Gallardo. They had runners on second and third in the first inning, but Gallardo struck out Conor Jackson and Mark Reynolds to end the threat. They also stranded two in the second.
Again, the D-backs stranded two in the fourth and fifth innings, but by that time, the game had been broken open by Fielder's bases-loaded double in the fourth.
Gallardo (5-3) came into the game having allowed 18 runs over his past two outings, but looked more like the hurler that had a 2.47 ERA in his first seven starts of the season. He allowed just five hits and one walk over six scoreless innings, striking out six.
"We did have him on the ropes early on," said Melvin. "He didn't have his best command early, but he found it. His velocity went up and his strikes went up."
Carlos Villanueva worked the final three innings to complete the shutout for his first save of the season.
By the end of the contest, the D-backs were using infielder Jeff Cirillo to mop up with a scoreless ninth.
"He hopefully lightened the mood a little bit, and we didn't have to use [another pitcher]," said Melvin. "We just move on."
If there's any consolation in the defeat, it's that since the All-Star break, the D-backs have gone on some mini-runs following games in which they were on the wrong side of a lopsided score.
They lost, 10-1, to Milwaukee on July 19. Two games later, they started an eight-game winning streak. They dropped a 14-0 decision to Atlanta on July 29, and won their next two, before dropping an 11-0 game to San Diego on Aug. 2. They followed that game up by winning seven of eight. After a 14-5 loss to Florida on Aug. 14, they won four in a row.
With their lead in the National League West standings at 3 1/2 games and their next 15 games against teams currently over .500, the D-backs would certainly like another run to start on Tuesday night.
As Orlando Hudson put it: "You just come back tomorrow and see what you can do."