The Giants took the series opener 3-0 on Tuesday, with two runs coming on Thairo Estrada's ninth-inning double
San Francisco has won 13 of its past 15 games overall and 15 of its past 17 road games.
The Blue Jays fell to 2-2 to open a nine-game homestand
Kevin Gausman, a former Giant, allowed one run in six innings on Tuesday, striking out 12. His seventh strikeout of the game came in the fourth inning and was the 1,500th of his career.
The Giants got five-plus solid innings from left-hander Alex Wood. He followed opener Ryan Walker, who worked out of a first-inning jam
"I thought it was a really good outing for Alex," Giants manager Gabe Kapler said. "(We) had a chat about it and decided it was best for this start (to use an opener). We'll just evaluate it each time out.
Wood said that he was more upright in his delivery and that contributed to his improved performance.
Toronto went 1-for-12 with runners in scoring position.
"We had our chances and they pitched well and got out of those jams," Gausman said.
Former Giants first baseman Brandon Belt was 1-for-4 with a double as Toronto's designated hitter
"It's baseball. I've played with a lot of guys that moved on," Belt said. "I've had a lot of my friends go to other teams, so you always know that there's a chance that you're not gonna -- in fact it's likely -- that you're not gonna be on the same team your whole career.
"Strange, but I've had a lot of fun over here. I was fortunate enough to get with a really good team with a bunch of really good guys. I think that's made the transition a lot easier."
Toronto shortstop Bo Bichette went 3-for-4 with a double in the series opener. He extended his hitting streak to 12 games, during which he is 18-for-50 (.360) with nine doubles and four RBIs.
The only run against Gausman came on a fifth-inning double by Patrick Bailey. The San Francisco catcher, who also threw out a runner trying to steal second, is on an eight-game hitting streak. He is batting .345 (10-for-29) with six RBIs during that span.
Giants infielder Wilmer Flores was reinstated from the injured list on Tuesday and infielder Isan Diaz was optioned to Triple-A Sacramento. Flores had been sidelined since fouling a ball off his left foot during an at-bat at Dodger Stadium on June 16. Imaging showed no structural damage, but he was placed on the IL the next day with a left foot contusion
Flores is batting .258 with seven homers and 23 RBIs this season. Diaz appeared in two games for San Francisco, going 0-for-8.
--Field Level Media