Barry Zito, 36, a non-roster invitee who is attempting a comeback after not pitching last season, retired the first five batters he faced, then hit Chris Coghlan with two outs in the Chicago second to set up Mike Olt's two-run homer. Ryan Sweeney followed with a single off Zito, who got Junior Lake to ground out and end the inning.
Travis Wood, battling for the fifth starter spot in the Cubs rotation, struck out two of the six batters he faced in his first outing. An All-Star in 2013, Wood scuffled last season, posting an 8-13 record and 5.03 ERA.
"You always learn more when you fail than when you succeed, and I learned a lot last year about how to go about when you fail, picking yourself back up and getting back after it," Wood said. "That's what we took into the offseason."
He heard that Maddon had named four starters and that Wood was not included in the quartet. The news just motivated Wood even more.
"There is [a purpose] -- the purpose is to not have a year like last year," Wood said. "I know I'm a good pitcher and just have to get back to the basics of attacking the zone and trusting your stuff."
Oakland tallied with one out in the seventh against Donn Roach on Luke Carlin's RBI single and tied the game in the eighth on Rangel Ravelo's one-out RBI double off Francisley Bueno.
The Cubs wore No. 14 caps and had a moment of silence before the game to pay tribute to Hall of Famer Ernie Banks, who died in January.
A's up next: Rotation candidate Kendall Graveman, one of four players sent to Oakland in the Josh Donaldson trade, makes his debut in green and gold in a start against the host D-backs at Salt River Fields on Friday. Josh Phegley, expected back in the A's lineup following the birth of his daughter, will be his batterymate. First pitch is scheduled for 12:10 p.m. PT.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.