Arizona won for the eighth time in Davis' nine starts since the All-Star break in the left-hander's seventh quality start over that period.
Davis chalked up his poor outing against the Brewers to just being one bad start, but in the four days since that appearance he worked with pitching coach Bryan Price on his mechanics because he was flying open. The adjustments helped slow the game down for Davis, who allowed six hits and tied a season high by striking out eight while walking one.
"My control was a lot better, and I wasn't falling behind and was able to get ahead, stay ahead and put them away," Davis said. "I just made my pitches when I had to."
In contrast, Davis often fell behind against the Brewers, leading him to throw three pitches down the middle that were hit over the fence. This time, Davis got ahead early, throwing 67 of his 104 pitches for strikes, and expanded the plate from there on a night when he had everything working.
Melvin said Davis' astute preparation habits help him put bad outings out of his mind, because the lefty can submerge himself in the next game plan instead of concentrating on what went wrong.
"We have confidence in him," Melvin said. "He just had a bad game [against Milwaukee]. His command was bad, the ball wasn't coming out of his hand nearly as well. It was just one of those games. It just seems like it was one of those games where he didn't have his good stuff, whether it was mechanically or whatever, and then rebounded because we can't afford for him to go into a mini-slump here where we are right now."
Conor Jackson provided all the support Davis needed by knocking out a two-run homer following a two-out single from Eric Byrnes in the fourth. The D-backs managed just two more hits off Chicago starter Ted Lilly (13-7) in his six innings of work.
Justin Upton celebrated his 20th birthday with a run-scoring double, his first RBI since Aug. 15, on a hit Melvin called "enormous" for the youngster's confidence, in his first multi-hit game since Aug. 7, a span of 50 at-bats.
"Games like that, a lot of times it's one swing of the bat," Melvin said. "[Jackson's] hit was big, Upton's hit was big, and usually in games like that the team who gets the hits with runners in scoring position wins."
The bullpen took it from there, as Brandon Lyon broke Luis Vizcaino's single-season club record with his 26th hold, and Jose Valverde finished the game with his Major-League leading 39th save.
After retiring the first two in the eighth, Lyon allowed a single to Derrek Lee that brought up Aramis Ramirez, who had hit a three-run homer off Lyon on July 20. Lyon walked the Chicago cleanup hitter on five pitches to bring the go-ahead run to the plate in Craig Monroe, before striking him out to end the threat.
"I knew probably in that situation the pitches I was going to use," Lyon said about the Ramirez at-bat. "Right there, I wasn't going to give in at all if the situation came up again, even though you're putting the go-ahead run at the plate. A situation like that, I'm not going to let him beat me."
The D-backs also got a boost from the fourth-biggest crowd of the season, an effort Melvin compared to the final game of the Red Sox series, when the Arizona faithful appeared to drown out those from Boston.
The support helped the D-backs maintain their two-game lead in the National League West over the Padres, despite having lost four of five entering Saturday.
"It's awesome," Upton said. "People come out to support us, and it's a big series. The Cubs are a good team, and they're leading their division, so for them to be out there it was definitely helpful."