SAN FRANCISCO -- Pablo Sandoval was back, and so was some of the San Francisco Giants' old magic Saturday night at AT&T Park.

Jarrett Parker hit a walk-off infield single with two outs in the bottom of the 10th inning, lifting the Giants to a come-from-behind, 5-4 victory against the Arizona Diamondbacks

But it was Sandoval, playing his first game for the Giants since 2014, who ignited a three-run rally in the seventh inning that made Parker's game-winning heroics possible.

The Giants trailed 4-0 entering the bottom of the seventh, but Sandoval, whose contract was purchased from Triple-A Sacramento on Saturday, lined a leadoff double off right-hander Taijuan Walker.

Parker brought Sandoval home with a double off the right-field wall, and Pence crushed Walker's 1-1 curveball into the left-field seats for a two-run shot, making it 4-3.

"That kind of woke us up because we looked dead in the water." Giants manager Bruce Bochy said of Sandoval's double. "Walker was throwing the ball well and we just couldn't do much with him. A nice piece of hitting by Pablo going the other way. He smoked it to get a double. And getting that first run just does a lot for a club. Of course. Pence followed that with the home run.

"At that point it's a different feel in the dugout, a lot of life. I wasn't surprised how we found a way to tie that ballgame."

The Giants pulled even with a run in the eighth. Pinch hitter Kelby Tomlinson lined a leadoff single off left-hander Andrew Chafin and moved to third on Brandon Crawford's single to right center. Buster Posey pinch hit for Sandoval, and Diamondbacks manager Torey Lovullo countered with right-hander David Hernandez. Hernandez got Posey to ground into a double play, but Tomlinson scored to make it 4-4.

Then in the 10th, Denard Span led off the inning with a double to deep right off reliever T.J. McFarland. Tomlinson was intentionally walked, and Span moved to third when Crawford grounded into a double play. After Posey was intentionally walked, Parker grounded an infield single up the middle that second baseman Adam Rosales fielded far behind second base after a long run. Parker easily beat Rosales' desperation throw, and Span raced home to score.

"That was a team effort tonight," said Parker, who made a spectacular sliding catch in foul territory down the left-field line in the second inning. "Walker had done a good job, shutting us down for the first part of the game and then Pablo comes up and gets a big knock and gets things going. Then hunter got a big knock too."

The home run was Pence's ninth of the season but first at AT&T Park and it ended Walker's night.

The Diamondbacks dropped to the second wild-card spot in the National League, one-half game behind Colorado and five ahead of Milwaukee.

"It's' tough to absorb," Lovullo said of the loss. "I feel like we did a lot of things right early and we put ourselves in a very good position to win this game. Taijuan was cruising. He had a three-hit shutout and he worked into the seventh inning.

"It happened very quickly, but I thought we did enough at the right times to put ourselves in a position to win. We just couldn't get the big hit at the right time."

McFarland said he made one bad pitch in the 10th, and Span made him pay.

"I left something up and he hit a fastball in pretty well," McFarland (4-4) said. "That set up the inning. Obviously when you have a guy on second and nobody out, percentages go up to score. I made a pitch to Crawford and got the double play.

"Honestly, I made the pitch I wanted to make (to Parker) there at the end and it just found a hole. It's just one of those things where it found the perfect spot."

Hunter Strickland (2-2) pitched a scored 10th inning for the victory.

David Peralta went 3-for-6 with a double, an RBI and a run for the Diamondbacks, J.D. Martinez went 3-for-4 with an RBI double, a triple and a walk.

Walker allowed three runs on six hits over six innings. He struck out six and walked none in a no-decision. Walker hasn't won a decision since June 21 at Colorado. He's 0-2 with five no-decisions over his past seven starts.

Giants rookie right-hander Chris Stratton allowed three runs, two of them earned, and five hits over five innings in his second career major league start. Stratton (right calf strain), who was activated from the disabled list Saturday, struck out four and walked four in a no-decision.

After Stratton exited, Kyle Crick allowed one unearned run over two innings. Cory Gearrin pitched a perfect eighth inning and Sam Dyson a scoreless ninth, despite loading the bases. Dyson retired Ketel Marte on a ground ball to end the threat.

NOTES: Giants 1B Brandon Belt (concussion) was placed on the seven-day concussion disabled list Saturday. Belt was hit in the head by a 79 mph curveball by Diamondbacks LHP Anthony Banda in the sixth inning Friday night and left the game. ... Giants 3B/1B Pablo Sandoval's contract was purchased from Triple-A Sacramento, and he started at third base and hit cleanup against Arizona. Sandoval played his first seven major league seasons with the Giants, from 2008 to 2014. Sandoval signed a minor league contract with the Giants on July 22 after being designated for assignment by the Red Sox on July 14. ... Giants RHP George Kontos was claimed off waivers by the Pittsburgh Pirates, ending his six-season run with San Francisco. ... Arizona INF Ketel Marte, who was reinstated from the bereavement list on Friday but did not play, started at shortstop and went 1-for-4 with a doubleSaturday. Marte traveled to the Dominican Republic after his mother died in a car accident.