Giancarlo Stanton homered off Santiago Casilla in the 10th inning, and the Miami Marlins beat the San Francisco Giants 3-2 on Wednesday night after blowing a two-run lead in the ninth.

Stanton sent a 2-2 slider from Casilla (1-0) into the left-field bleachers for his third home run of the season. The long ball followed a wild ninth that saw struggling Marlins closer Heath Bell blow his fourth save in seven chances.

Carlos Zambrano pitched seven scoreless innings, and Steve Cishek (3-0) relieved Bell for the final six outs to give Miami its second straight win in San Francisco.

Giants starter Barry Zito tied a career-high with seven walks and lasted only 3 2-3 innings. Two defensive mishaps by the Giants accounted for Miami's first two runs.

Another series of mistakes by Miami's new high-priced closer almost turned into another loss.

Brandon Belt lined a double to left leading off the bottom of the ninth. Joaquin Arias singled home Belt, and Buster Posey followed with another hit to chase Bell.

After Cishek struck out pinch-hitter Brett Pill, Gregor Blanco bunted down the first-base line. Gaby Sanchez fielded the ball cleanly but had no play, allowing Arias to score the tying run.

Angel Pagan grounded into a fielder's choice and Melky Cabrera had an infield single to short that loaded the bases. Ryan Theriot's weak groundout to second sent the game to extra innings, where Miami backed its struggling closer.

The big man at the back end of the bullpen has looked nothing like his old self.

The 34-year-old Bell, who received a $27 million, three-year contract with the suddenly big-spending Marlins in December, had 40-plus saves each of the past three seasons with the San Diego Padres, including 43 in 48 chances last year with a 2.44 ERA. He leads the majors with 134 saves over the past three-plus seasons. Bell's ERA so far this season is 11.74.

In contrast, Zito reverted back to his wild ways after a surprisingly strong April.

The slow-throwing left-hander's curveballs danced anywhere but in the strike zone. He threw 60 pitches in the first two innings — finishing with 91 total, only 50 for strikes — and his defense did him no favors.

With one out and the bases loaded in the first, Brandon Crawford mishandled a grounder to short by Omar Infante. Crawford threw out the runner at second, but Joaquin Arias' relay to first was too late, allowing Emilio Bonifacio to score.

Zito walked two more in the second and again nearly worked out of a jam. Instead, Arias bungled a grounder by Bonifacio off his glove for an error, and Gaby Sanchez scored to give Miami a 2-0 lead.

The poor pitching washed away what had been a surprisingly solid May for Zito.

The 2002 AL Cy Young Award winner had allowed only six walks — and six runs — in his four previous starts this year, including a four-hitter at Colorado on April 8. Only time will tell whether his sharp opening month or latest outing was a fluke.

Same goes for Miami's suddenly winning ways.

The Marlins had lost eight of nine before traveling to the West Coast. A new month has been kinder so far to rebranded Miami.

Zambrano quieted San Francisco's hitters, not allowing a single hard-hit ball in spacious AT&T Park. He allowed five hits and struck out five in seven scoreless innings.

Miami finished last in the NL East with an 8-14 record in April, mostly due to an anemic offense, and motor mouth manager Ozzie Guillen made more headlines for his political views — telling Time magazine he admired Cuban dictator Fidel Castro — than anything to do with baseball.

The Marlins are 2-0 in May.

NOTES: Giants manager Bruce Bochy was shocked and saddened to learn of the apparent suicide of former San Diego Chargers linebacker Junior Seau. Bochy became friends with Seau when he managed the San Diego Padres from 1995-2006. "He's a guy when he walks in a room, he kind of takes over, he's laughing and just enjoying life. ... for this to happen, it shocks me," he said. ... Giants 2B Freddy Sanchez, recovering from another setback on his surgically repaired right shoulder, took infield practice and played long toss with OF Aubrey Huff before the game. Huff is on the 15-day disabled list with what the team has called an anxiety disorder. ... Marlins LF Logan Morrison had the day off with a lefty starter on the mound, giving him a chance to rest his nagging right knee. Austin Kearns started in his place.