The Rockies have won four in a row following a three-game sweep against the visiting Miami Marlins over the weekend.
Colorado had been stumbling ever since losing the final six games heading into the All-Star break to fall a game under .500. The Rockies continued to slide coming out of the break, falling as far as 14 games under .500 before their latest winning streak.
"We put record aside, stats aside. We're just having fun, trying to play more loose," said Rockies second baseman Garrett Hampson, who collected his first walk-off RBI in a 7-6 win in 10 innings on Sunday.
Meanwhile, the Diamondbacks ended a four-game losing streak with a 6-1 win against the visiting San Francisco Giants on Sunday.
"Pretty nice to come out on the other side of things after several games where we played good baseball and we've suffered, lost those games," Arizona manager Torey Lovullo told reporters after Sunday's win. "I felt we tightened some things up today."
Gallen (2-3, 2.58 ERA) has made two starts for Arizona since he was acquired from the Marlins at the end of last month. He faced the Rockies in his last outing on Tuesday and allowed two runs and nine hits in four innings, making him ineligible for the win in the 9-3 victory.
Gallen made his debut for the Diamondbacks by throwing five shutout innings and allowing one hit in a 6-1 win against the Philadelphia Phillies on Aug. 7.
He will need to be extra careful with red-hot Rockies third baseman Nolan Arenado, who has four home runs during the team's winning streak. He hit his 29th and 30th homers on Sunday, joining Vinny Castilla and Todd Helton as the only Rockies with five or more seasons of at least 30 home runs.
Gonzalez (0-4, 6.57 ERA) was recalled from Triple-A Albuquerque on Friday and will be looking for his first major league win since Sept. 22, 2015.
Gonzalez, a first-round draft pick of the Texas Rangers in 2013, had a remarkable start to his career, combining for 14 2/3 scoreless innings in his first two major league outings and nearly becoming the first Rangers pitcher to win his first three starts.
He missed all of the 2016 and 2017 seasons after undergoing Tommy John surgery, however, and has lost seven straight decisions since his last victory.
The Rockies also placed closer Scott Oberg on the 10-day injured list after he underwent surgery on Saturday night because of a recurrence of blood clots in his right arm. Wade Davis, who lost his closer's role to Oberg earlier this season, filled that spot on Sunday and blew the save in the ninth inning.
--Field Level Media