Feldman was perfect again in the third inning and struck out Ryan Roberts for the final out of the frame.
"Overall, it was a very positive outing for me," Feldman said. "I was able to throw my changeup a lot and I had some good results with that. It was a good day."
The Rangers scored twice in the first inning to take an early lead. Texas second baseman Ian Kinsler led off with a double and scored on double by Michael Young for the first run. David Murphy scored from third on a sacrifice fly by Mike Napoli.
Saunders eventually walked Conor Jackson but did not allow another hit in the frame.
The D-backs' left-hander retired the first two batters he faced in the second, but Kinsler hit a double and came home for the Rangers' third run on a single by Murphy. Young followed with a single to move Murphy to third base, but he did not advance. Saunders struck out Napoli to end the inning.
Saunders gave up a pair of two-out singles to Engel Beltre and Zach Zaneski, the Nos. 7 and 8 hitters in the Texas order, respectively, in the bottom of the third, but escaped the inning unscathed.
Kubel hit a two-out home run to right field in the fourth for Arizona's first run. He also homered in the fifth inning.
Chris Jakubauskas replaced Saunders to start the fourth inning and struck out Kinsler on his way to retiring the side in order. In all, Saunders threw 64 pitches, 40 of which were strikes.
"Leg feels great," said Saunders, who was forced to leave his last start in the first inning after being hit by a line drive in the left shin. "The only thing today I was a little frustrated with was fastball command. I threw some good ones and then when I didn't locate it very well, they hit it where we weren't."
Kinsler hit a two-run homer for the Rangers in the sixth and finished 3-for-4.
Up next for D-backs: The D-backs play split-squad games Sunday. They will host the A's at Salt River Fields. A pair of former A's are slated to pitch with Trevor Cahill getting the start and lefty Craig Breslow expected to appear in relief. The other half of the team will travel to Goodyear to take on the Reds, with top left-handed pitching prospect Tyler Skaggs starting.
Up next for Rangers: Matt Harrison pitches Sunday for the Rangers against the Cubs in the second game of their two-game series in Las Vegas, live on MLB.TV at 3:05 p.m. CT. But the Rangers also have a split-squad game with the Brewers in Maryvale at 2:05 p.m., and Robbie Ross will start that one. Ross, a rookie left-hander, is mounting a challenge to win a spot in the bullpen, and the Rangers want to see him against Major League hitters at the beginning of the game rather than Triple-A or Double-A hitters in the later innings.