A steady downpour forced a delay of more than an hour, and the ground crew covered the infield with a silver tarp before officials decided to call off the game, sending home a crowd that was expected to be near 30,000.
"The field was bad, and we have new turfs down too, and the water probably stands on that more too," A's manager Bob Melvin said. "We did a lot to try to get this game in ... but it didn't make sense with the conditions and potential of some even more rain. You're potentially putting guys at risk, injury-wise."
Oakland opens the regular season Monday at home against the Cleveland Indians. San Francisco plays its opener in Arizona.
The A's later announced that fans who bought tickets for the game will be allowed to redeem the paid value of the tickets to a future regular-season game.
Giants: RHP Ryan Vogelsong's turn in the rotation came up Saturday against the A's, but he stayed in Arizona to ensure he'd get his scheduled work in. San Francisco had called up lefty Edwin Escobar from the minor league camp to start in Vogelsong's absence before the game was called off.
LHP Madison Bumgarner will make his first opening day start for the Giants in Arizona. Bumgarner went 3-0 with a 1.19 ERA in five spring starts.
Athletics: RHP Dan Straily didn't let a little rain cramp his day. Long after the parking lots emptied and while workers continued to sweep water off the infield tarp, Oakland's scheduled starter got his work in by throwing off the bullpen mound while Melvin looked on.
Right-hander Sonny Gray starts for the A's in their opener against the Indians. Gray is the ninth different opening day starter in nine years for Oakland.
Giants: 2B Marco Scutaro and LHP Jeremy Affeldt were placed on the 15-day disabled list in a pair of moves that had been expected. The move for Scutaro, who has a lower back strain, is retroactive to March 21, while the one for Affeldt (right knee sprain) is retroactive to March 23.
Athletics: RHP A.J. Griffin (flexor muscle strain), RHP Ryan Cook (shoulder tendinitis), RHP Fernando Rodriguez (Tommy John surgery) and OF Craig Gentry (lower back strain) were put on the 15-day disabled list. Cook, however, remains on track to rejoin the big league club in the first week of April.
Giants: RHP Juan Gutierrez and INF Brandon Hicks were added to the 25-man roster after having their contracts purchased by the big league club. Additionally, OF Tyler Colvin was reassigned to Triple-A Fresno, RHP Derek Law was reassigned to Double-A Richmond and OF Roger Kieschnick was designated for assignment.
Athletics: C Stephen Vogt, who played a key role as a backup during Oakland's AL West title run in 2013, was optioned to Triple-A Sacramento along with LHP Joe Savery and IF Jake Elmore. OF Michael Taylor was designated for assignment, non-roster invitee Billy Burns was reassigned to the team's minor league camp and OF Sam Fuld had his contract purchased from Sacramento.
According to a team spokesman, this marks the first time since 2006 that the A's won't have a rookie on their opening day roster.
Coaches from the A's were sent scrambling after toilets in the home clubhouse backed up and overflowed early Saturday.
It was the latest in a series of plumbing problems that plague the stadium built in the late 1960s.
In September, A's players reported foul smells from the bathroom end of their dugout. That came after a clogged pipe caused a sewage backup and flooding on the bottom floor of the ballpark in June, sending the Seattle Mariners and A's scrambling around in towels and heading for higher ground in the Oakland Raiders' locker room.