Cahill, who was recently named to start the second game of the D-backs' regular season opening series in Australia, wound up allowing six runs on eight hits in lasting just three innings.
Arizona's offense got going right from the get-go as well, as the D-backs used four straight hits to start their half of the first against Oakland's Sonny Gray in what would prove to be his only inning of work.
Gerardo Parra had an RBI single in the inning, while Martin Prado added a two-run double and Matt Tuiasosopo drove home the final run of the frame with a groundout. Parra added another RBI single in the fifth.
The A's tied the game at 4 in the second when Sam Fuld, who is battling for one of the final bench spots, hit a solo homer to right.
One inning later, Brandon Moss smacked a two-run homer to right to put the A's up, 6-4. Josh Reddick then doubled in Coco Crisp in the fourth.
Luke Montz drove in Addison Russell on a sacrifice fly in the ninth to knot the score after the D-backs posted a three-run eighth.
Athletics up next: Lefty Scott Kazmir will make his highly anticipated Cactus League debut at home against the D-backs beginning at 12:05 p.m. PT on Friday, available on a webcast exclusive to athletics.com. Kazmir impressed coaches on Sunday with a 45-pitch, three-inning simulated game, using all of his pitches and showing good life on his fastball. The southpaw, who signed to a two-year, $22 million deal this winter, will have more than a few regulars behind him, including Jed Lowrie, Josh Donaldson, Yoenis Cespedes, Josh Reddick, Derek Norris and Alberto Callaspo, who will make his debut at first base.
Steve Gilbert is a reporter for MLB.com. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.