SAN FRANCISCO -- When teammate Andrew Susac lined a one-out single in the bottom of the ninth inning Sunday, San Francisco Giants utility infielder Matt Duffy started preparing to be a hero.

Despite the fact his possible at-bat was still five hitters away.

"I was rooting for the guys to get it down before that," he said. "But if it got to me, I was going to be ready."

Duffy wound up getting that shot with two outs and the bases loaded in a tie game and came through with a walk-off RBI single, capping a two-run rally that lifted the Giants to a 3-2 win over the Miami Marlins.

Center fielder Gregor Blanco had three hits, including a pair of doubles, and right fielder Justin Maxwell threw out a runner at home plate in the top of the ninth for the Giants, who salvaged a split in the four-game series.

The Giants' rally came against Marlins closer Steve Cishek, who San Francisco had never scored an earned run against in 15 previous meetings.

Called upon to protect a 2-1 lead, Cishek (1-2) struck out Maxwell to open the ninth. But Susac singled and Blanco doubled off the fence in right, putting the potential tying and winning runs in scoring position.

The Marlins elected to walk pinch-hitter Buster Posey intentionally to load the bases, and Cishek got within one out of his fourth save by striking out pinch-hitter Angel Pagan.

But Cishek then walked left fielder Nori Aoki on a full-count pitch to tie the game, and Duffy followed with a solid shot to left field that scored Blanco with the game-winner.

The blown save was Cishek's third of the season.

"I had a good view of his whole at-bat," Duffy, who was standing in the on-deck circle, said Aoki's walk. "I saw all (Cishek's) pitches. That definitely helped."

Also helping was the fact Duffy, who never previously had recorded a walk-off hit, insisted he wasn't nervous. That's because, five batters earlier, he projected ahead to see if it were even possible for him to bat in the ninth without the Giants haven't already won the game.

"I did the math," he said, an equation that assured he could only come to the plate if one run had scored, the bases were loaded and there were two outs. "Normally the adrenaline would be flowing in that situation. But I had time to prepare for it."

The walk-off win was the Giants' fourth of the young season.

"That's one thing you can say about the Giants the last couple of years: We battle back," said first baseman Brandon Belt, who had two of the Giants' 10 hits. "We did a great job of that today."

Added Duffy, "Comebacks like that don't just happen with one guy. Get one guy up, then get the next guy up. Finally it got to me."

Right-hander Santiago Casilla (4-0), the fourth Giants pitcher, was credited with the win.

The Giants' uprising came after the Marlins had scored in the eighth to take a 2-1 lead. Pinch-runner Donovan Solano slid home safely after a Sergio Romo wild pitch with two outs to break a 1-1 tie.

"We caught a break with the wild pitch," noted Marlins manager Mike Redmond. "It was all lined up."

Miami nearly added an insurance run in the ninth, but left fielder Christian Yelich was thrown out at home plate by Maxwell on a single by first baseman Michael Morse.

Susac appeared to be illegally positioned in the baseline while waiting for Maxwell's throw, forcing Yelich to maneuver around him and miss the plate on first swipe. But Redmond chose not to challenge the play.

"I don't know if you've followed us," he said of his personal history in challenging such calls, "but we haven't had a whole lot of success on that play."

When it was mentioned that Giants manager Bruce Bochy often has successfully got out calls overturned because of the new rule, Redmond responded, "They must like him, obviously, because we haven't had much success."

Right-hander Mat Latos pitched seven strong innings without getting a decision and second baseman Dee Gordon returned from a two-game absence to contribute a pair of doubles for the Marlins.

Latos allowed seven hits and one run in his seven innings. He struck out five and did not walk a batter.

Giants starter Ryan Vogelsong, who also did not get a decision, had his second consecutive strong outing, limiting the Marlins to one run on four hits in seven innings. He struck out five and did not walk a batter while lowering his ERA to 5.67 after it had been 9.31 before his previous start.

NOTES: The Giants lead the majors with nine one-run wins. ... The Marlins had been 14-1 when leading after eight innings. ... Giants C Buster Posey, SS Brandon Crawford and CF Angel Pagan all made pinch-hitting appearances late in the game after not starting. ... Marlins RF Giancarlo Stanton did not play in the series finale to get a rest. Stanton not only had played every inning this season, but had not had a healthy non-start in almost a year (May 18, 2014, also in San Francisco).