Arizona (56-78) moved three games in front of Colorado with a 5-2 win Friday as Jake Lamb provided the go-ahead grand slam in the eighth inning for his second home run in 16 career games.
The victory was the Diamondbacks' eighth in 25 games this month but seventh in the last eight matchups with the Rockies (53-81), who are tied with Texas for MLB's worst record.
Nuno (0-3, 3.54 ERA) is looking to earn his first win since June 27, when he was with the Yankees. The left-hander has received 18 runs of support in nine starts since being acquired July 6.
He's posted a 2.70 ERA in his last three outings, yielding two runs and two hits in a career-high 7 1-3 innings last Saturday as Arizona beat San Diego 5-2 after losing each of his first eight starts.
"I just try to go deep in the games," Nuno said. "The outcome has been unlucky, but just keep on fighting and I'll get it."
Nuno will make his first start against Colorado, which has lost four straight and 27 of 31 on the road. The Rockies have totaled five runs and 16 hits in those four consecutive defeats.
Matzek (3-9, 5.14) will pitch in Arizona for the second time this month after the rookie left-hander gave up three runs, four hits and walked a career-high five in five innings of a 5-3 loss Aug. 8.
He snapped a five-start losing streak Monday with a 3-2 win in San Francisco, allowing two runs and striking out seven in seven innings. Matzek had an 8.06 ERA in his previous five appearances and was 0-5 with a 6.23 ERA in his prior seven on the road.
"It's good to go out there and help the team win," he said.
Matzek has thrown a career-high 150 2-3 innings for the Rockies and Triple-A Colorado Springs, but there are no plans to limit him the rest of the season, manager Walt Weiss told MLB's official website.
"Arm feels fine," Matzek said. "I had a good offseason this past offseason and built my body up to feel strong, so I'm feeling pretty good right now."
Miguel Montero hit a three-run homer off Matzek earlier this month, one of his three in his last 50 games. He's 4 for 23 in his last seven contests.