SAN FRANCISCO -- Vladimir Guerrero Jr. received some advice from his Hall of Fame father after hitting the first two home runs of his career. In return, the younger Guerrero plans on sending his father a few mementos from his historic night.

Guerrero homered twice to become the third-youngest player to hit his first two major league homers in the same game, and the Toronto Blue Jays beat the San Francisco Giants 7-3 Tuesday night.

Guerrero, who finished with three hits and four RBIs, became the youngest in franchise history to go deep as the Blue Jays won the opener of a six-game trip after losing five of six on a homestand in which they totalled eight runs.

"He just said like he always told me, 'Don't look for home runs. They're going to come,"' Guerrero said through a translator. "I'm going to give both balls and the bat to my dad. I'm going to keep using everything that I used today except the bat that I really want to give to my dad."

The touted 20-year-old Guerrero homered in the first inning against Giants opener Nick Vincent (0-2), his first in 14 big league games. His drive to straightaway centre was measured at 111.3 mph and travelled an estimated 438 feet.

"He was talking about it during batting practice and he did it," Toronto manager Charlie Montoyo said. "We knew that was coming. He's that good. He could carry a team if he gets hot. He can do stuff like that."

The Toronto slugger had a hard-hit single in the second then added an even more impressive blast in the sixth off Reyes Moronta, a three-run drive estimated at 451 feet.

The crowd at Oracle Park let out a collective gasp as the ball sailed over the wall in left-centre. Winning pitcher Trent Thornton even got caught up watching.

"I was on second base and I'm just watching it go and go, and I'm like, 'Wait, I gotta run,"' Thornton said. "He had a great game. That was just a lot of fun."

The only players younger than Guerrero to hit their first two home runs in the same game were Brian McCall in 1962 (19 years, 248 days) and Manny Machado in 2012 (20 years, 35 days).

Two-sport star Danny Ainge was the youngest Blue Jays player to homer, doing so on June 2, 1979 at 20 years, 77 days old. Guerrero is younger by 18 days.

Guerrero grounded out in his final at-bat. He entered the day batting .191 with one RBI.

"He wasn't pressing," Montoyo said. "He just plays and he has fun. He's an even-keeled kind of kid."

The Guerrero family already had long-ball history at Oracle Park -- the elder Guerrero won the 2007 Home Run Derby at the waterfront stadium.

"This kid is going to be a great player, he really is," Giants manager Bruce Bochy said. "You saw the bat speed, you saw how fast the ball comes off his bat. I've seen his dad hit balls like that."

Thornton (1-4) pitched three-hit ball into the sixth inning for his first major league win. The rookie right-hander struck out seven and overcame five walks. Thornton also singled twice to help the Blue Jays break out of their offensive funk.

Toronto got an overturned replay and added two runs in the first following Guerrero's first home run.

Freddy Galvis hit an RBI double that fell just over the glove of charging right fielder Steven Duggar but was ruled foul by first base umpire Adrian Johnson. After Montoyo asked for a replay, a brief review was held and the call was overturned. Bill McKinney then doubled in Galvis.

Pablo Sandoval homered for San Francisco.

The Giants used an opener for the first time. Vincent allowed three runs and four hits in one inning in his second career start.