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.
Up next for the D-backs: The D-backs will play the A's for the second straight day Friday at 1:05 p.m. MST, but this time they will travel to Phoenix Municipal Stadium. Left-hander Wade Miley will start for the D-backs. Addison Reed, who is battling J.J. Putz for the closer's job, is also slated to pitch.
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.