San Francisco slugger Pablo Sandoval hit a spectacular three home runs on Wednesday to lead the Giants to an 8-3 victory over Justin Verlander and the Detroit Tigers in game one of the World Series.

Venezuela's Sandoval smacked a solo shot in the first inning, a two-run blast in the third and another solo homer in the fifth to become just the fourth player to hit three home runs in one game of Major League Baseball's best-of-seven championship showcase.

The feat put him in elite company alongside Babe Ruth - who did it twice - Reggie Jackson and Albert Pujols.

Of the group, Sandoval is the only one to homer in his first three at-bats of the game.

"Man, I still can't believe it," Sandoval said.

Sandoval's first two homers came off Detroit's vaunted ace Verlander, who made it through just four innings and 98 pitches and gave up five runs on six hits.

Verlander came into the contest with a 3-0 record and an 0.74 ERA, having struck out 25 batters while allowing only 10 hits over 24 1/3 playoff innings.

But the Giants wasted no time in pouncing on Verlander, whose team hadn't played since completing a sweep of the New York Yankees in the American League Championship Series last Thursday.

San Francisco came into the contest battle-hardened, having just won their third game in a row on Monday to cap an improbable comeback over St Louis in the National League Championship Series.

They are trying to claim their second title in three years, after winning it all in 2010.

Sandoval's two-out solo homer to centre field in the first inning proved to be a sign of things to come.

In his next at-bat, he belted a two-run homer as part of a three-run third inning for the Giants.

Angel Pagan came to the plate with two out and reached second base on a liner that was headed straight to Tigers third baseman Miguel Cabrera but instead hit the bag and flew away from him.

Marco Scutaro, the Most Valuable Player of the Giants' series victory over the Cardinals, then laced a single up the middle that scored Pagan and brought Sandoval to the plate.

After Verlander issued two balls to Sandoval, Tigers manager Jim Leyland headed to the mound for a chat. He opted to leave his ace in and Sandoval promptly sent the next pitch he saw over the wall to make it 4-0 for San Francisco.

Giants pitcher Barry Zito called it "awesome".

"To go up early in the game like that, get first blood, get the momentum going and then just to cap it off with a couple more and a single as well," he said of Sandoval's night. "Just a pleasure to be a part of it."

"You certainly tip your hat to what Sandoval did tonight," Leyland said. "It was unbelievable."

Sandoval's feat overshadowed Zito, who thwarted the Tigers with a mix of off-speed pitches and his curveball.