The win was the fifth in a row for the D-backs and their eighth straight at home as they improved to 49-48, the first time they've been over .500 since June 30.
After pitching well enough to win in his previous three outings, yet having an 0-2 record to show for it, Saunders picked up his first victory since June 10. The left-hander held the Rockies to just two runs on three hits over seven innings of work, while matching a career high with nine strikeouts.
"For me tonight it was just about getting ahead and throwing strikes," Saunders said.
It was Saunders' third start since coming off a stint on the 15-day disabled list.
"I like what I've seen so far in his first three starts," D-backs manager Kirk Gibson said. "I think he's getting stronger and stronger."
The only hitter in the Colorado lineup that Saunders had trouble with was Michael Cuddyer, who had two hits, both home runs.
"I just have to stay out of the middle of the plate with that guy, I guess," Saunders said. "I was trying to make good pitches to him and just made two mistakes and he made me pay for it."
Other than the pair of homers to Cuddyer, the only other Rockies player with a hit was relief pitcher Josh Roenicke.
"The curveball has been a lot better," Saunders said. "I've been working with [pitching coach Charles Nagy] in the bullpen the last couple of times and been just working on staying back and staying through it and staying on top of the baseball and it's been pretty good for me the last few starts."
The D-backs wasted some early opportunities against Rockies starter Edwar Cabrera, leaving six men on in the first three innings.
Finally, in the fourth inning, Arizona was able to break through as Stephen Drew and Willie Bloomquist each had RBI doubles to give the D-backs a 2-1 lead.
One inning later, Chris Young hit a two-run homer to put Arizona up 4-1.
Young continues to show signs of coming out of his slump. In addition to the homer, he had a single and drew a pair of walks.
"He's coming on," Gibson said. "He's getting his confidence back. You're seeing him taking pitches. He's taking a pitch properly and when some guy hangs it like he did tonight, then it's gone."
After a hot start to the season, Young found himself mired in a long slump after missing 28 games due to a shoulder injury.
In his last 25 plate appearances, Young is 8-for-20 and has drawn five walks.
"Seeing the ball a little better," Young said. "Honestly not thinking about mechanics at all, just trying to stay relaxed and square the ball up. It's just baseball, it's how it goes. You have your ups and downs, but you just keep showing up, keep showing up and keep throwing it out there and good things will happen. Just don't lose faith in yourself and you'll be alright."
The D-backs tacked on a pair of insurance runs in the seventh inning on a two-run single by Miguel Montero.