SAN DIEGO -- The San Francisco Giants had little trouble with the Padres while San Diego couldn't figure out Chris Heston.

The San Francisco rookie dominated the Padres, and the Giants hit three home runs while cruising to a 9-3 victory Tuesday night at Petco Park.

Heston (10-5), who threw a no-hitter earlier this year, was sensational through 7 1/3 innings. He allowed one hit, two walks and hit a batter while striking out six.

"He was really throwing the ball well, good sinker, good movement on his fastball," Giants manager Bruce Bochy said.

Padres starter Odrisamer Despaigne (3-7) was lifted before recording an out in the fifth. He was tagged for six runs on seven hits and two walks.

The Padres didn't get a hit until center fielder Melvin Upton Jr. opened the sixth inning with a broken-bat single to center field. His flare landed just beyond second baseman Joe Panik's glove as the barrel of the Upton's bat ended up wedged in the screen behind the plate.

"He was on it," Padres interim manager Pat Murphy said of Heston. "He made some great pitches, quality pitches."

Heston admitted he thought about another no-hitter.

"It creeps in your mind but you try not to think about that stuff because quicker than not you're probably going to eventually give up a hit," Heston said.

The victory snapped San Diego's season-high, five-game winning streak and the Giants' four-game losing streak at Petco Park. San Francisco has just five wins in its past 19 outings in San Diego.

Giants catcher Hector Sanchez stroked his second career grand slam in the sixth inning off reliever Dale Thayer, extending the visitors' advantage to 9-0. Sanchez's homer carried 428 feet deep into the right field seats, and he admired it with a bat flip.

"It's good to break out and get some runs here," Bochy said. "The long ball isn't something you don't expect here."

Thayer intentionally walked left fielder Gregor Blanco to load the bases, setting the stage for Sanchez's blast. Right fielder Hunter Pence and shortstop Brandon Crawford singled -- Crawford's third hit of the night -- before Blanco walked.

The benches and bullpens emptied in the eighth after Sanchez grounded out and exchanged words with reliever Shawn Kelley when returning to the dugout. No one was ejected.

"The players handle those things," Murphy said. "There were words exchanged."

The Padres scored three unearned runs in the ninth.

Heston retired the first 11 batters he faced. Right fielder Matt Kemp reached in the fourth after getting hit by a pitch in the left arm, the only San Diego runner through five innings.

Shortstop Brandon Crawford extended the Giants' cushion to 5-0 in the fourth when he hit a three-run homer off Despaigne. Crawford's 13th of the season came after third baseman Matt Duffy began the inning with a double and first baseman Brandon Belt walked.

Pence slammed Despaigne's 77 mph curveball 434 feet for a solo home run to open the second inning. Pence's fifth of the year gave the Giants a 1-0 lead. Belt and Crawford followed with singles, and Belt scored when left fielder Gregor Blanco hit into a double play.

"I think they hit the ball hard sometimes with two strikes," Despaigne said through a translator. "I hadn't pitched in 11 days and it was 17 days since my last start and I think that was the difference today."

Bochy was watching Heston stymie the Padres while thinking of Tim Lincecum's first no-hitter, which came at Petco in 2013. Heston threw 116 pitches before being pulled.

"That broken bat single there broke it up and that probably saved me," Bochy said. "Because his pitch count was going to get up there and I've been in that boat before here -- I let Timmy throw 148 (pitches)."

NOTES: Padres LF Justin Upton (oblique) was out of the lineup again Tuesday. But the club said it expects him to play during the homestand. ... San Diego RHP Brandon Morrow (shoulder) could be sent on a rehab assignment this weekend. ... Padres 2B Cory Spangenberg (knee) took pregame ground balls. ... Padres OF Wil Myers could start hitting later this week. ... Giants C Buster Posey did not play because of a tight hamstring, but he is expected to start Wednesday. ... Giants LHP Jeremy Affeldt (shoulder) threw a bullpen session. He could be activated this week. ... Giants RHP Tim Lincecum (arm, hips) won't throw for four days after receiving cortisone shots in his hips Monday.