OAKLAND, Calif. -- Stephen Drew singled in the go-ahead run in the top of the 11th inning and the Arizona Diamondbacks won their season-high fourth straight game, beating the Oakland Athletics 8-7 on Saturday night.
Jason Giambi hit his 400th career home run, becoming the 44th player in major league history to reach the mark. Jack Cust, Adam Kennedy and Nomar Garciaparra also connected as the A's pounded former ace Dan Haren, but still couldn't pull out the win.
Mark Reynolds added a two-run double in the 11th off Santiago Casilla, Oakland's seventh pitcher, and Tony Pena (4-1) pitched the 10th inning for the victory. Arizona rallied against loser Craig Breslow (0-1) and improved to 6-2 during its three-city road trip that winds up Sunday.
Chad Qualls finished for his 11th save in 12 chances, but not before giving up Kennedy's run-scoring double followed by Ryan Sweeney's infield RBI single. Jack Hannahan then grounded into a game-ending double play.
Giambi connected for the milestone drive leading off the fourth inning, hitting a 3-2 off-speed pitch into the right-field bleachers and watching the ball as it sailed out. Haren's four homers were a career high and doubled his previous season total.
The 38-year-old Giambi received a warm ovation from the crowd of 21,295 and then came back out of the dugout for a curtain call at the Coliseum. The solo shot put the A's up 3-1, then Kennedy homered two batters later. Garciaparra's sixth-inning solo shot made it 5-1.
That instant offense helped stake Edgar Gonzalez to a nice cushion in his Oakland debut while facing his former club, but the bullpen couldn't hold a four-run lead. Gonzalez made 35 starts for Arizona from 2003-2008, then signed a minor league deal with the A's in February. He had seven starts for Triple-A Sacramento before his callup Tuesday.
Giambi's fourth homer of the year also marked his 191st with the A's, tying Gus Zernial for ninth place in franchise history. Giambi returned to Oakland this year for a second stint following seven seasons with the Yankees.
Oakland lost its third straight and seventh in nine to fall a season-high 10 games under .500 at 15-25.
After Drew hit a sacrifice fly in the top of the first, Cust answered in the bottom half with a two-run homer.
Haren is winless in his last three starts. Traded to Arizona after the 2007 season, he dominated the A's when they met in interleague play last year.
Arizona loaded the bases with no outs in the eighth to chase Russ Springer, then former A's fan favorite Eric Byrnes hit a two-run single one out later off Andrew Bailey before Chad Tracy's tying two-run double.
Arizona leadoff man Felipe Lopez left with tightness in his left hamstring following his fifth-inning single and was listed as day-to-day. He doubled to start the game.