Conforto fielded four balls in Toronto’s five-run first inning, running into the wall in foul territory to make a catch on Matt Chapman’s fly ball.
Austin Slater pinch hit when Conforto’s turn came up for the first time in the top of the second inning.
Conforto signed a $36 million, two-year deal to play in San Francisco last January. He came in batting .236 with a team-high 12 home runs and 42 RBIs in 70 games.
Conforto hit .255 with 132 home runs and 396 RBIs over parts of seven seasons with the New York Mets before joining the Giants.
Giants’ Michael Conforto (left hamstring) leaves after 1 inning