Making his first appearance against the team that traded him away on April 2, the San Francisco center fielder opened the scoring in the second inning, hitting an RBI single to left field in the Giants' 7-6 victory on Tuesday night.
"I'm a hopeless romantic," Pillar said. "I was hoping for the stars lining up for a second and to get the opportunity to come up there with runners in scoring position in a tie game and you come up with a big hit."
Pablo Sandoval went 3-for-4 and homered for the first time this year, one of a season-high four home runs for offensively challenged San Francisco.
Joe Panik homered and drove in three runs, and Evan Longoria and Brandon Belt also went deep for the Giants, who came in 29th in the majors in batting and ahead of just one team in home runs. It was San Francisco's first four-homer game since July 4, 2018, against Arizona.
"It's got to do a lot for their confidence," manager Bruce Bochy said. "It starts to weigh on you a little bit when you haven't hit a home run."
Rowdy Tellez hit his first career grand slam for the Blue Jays, whose four-game winning streak was snapped.
Jeff Samardzija (2-1) allowed two earned runs in 5 1/3 innings, improving to 3-0 in four starts against the Blue Jays. He allowed five hits, walked one and struck out four. Will Smith worked a perfect ninth for his sixth save.
Samardzija said the Giants were happy to see the attention Pillar got upon his return to Rogers Centre.
"He should be a rock star," he said of Pillar. "Guys like that should be pushed more by this league, guys that play hard."
The Blue Jays trailed 7-2 before Tellez's one-out, bases-loaded bash in the eighth off Tony Watson, who stayed on and finished the inning. It was also Tellez's first career homer off a lefty.
"Mentally it's nice to have a good at-bat against a tough lefty out of the bullpen," he said.
Trent Thornton (0-3) lasted five innings in his fifth major league start, giving up four earned runs on six hits and striking out five.
"You know what I like about this team? We don't quit," Blue Jays manager Charlie Montoyo said. "You never see me smile after a loss but man, this is pretty cool. That's what I was thinking on the bench."
Belt's home run off Thomas Pannone, which hit the facade of the third deck in right field, was his fifth of the season, and it ended a run of 15 hitless at-bats against left-handed pitching.
Panik's solo shot in the fifth inning was his first of the year, and he doubled in two runs in the third. Sandoval slugged one over the center-field fence in the eighth.
Samardzija had retired 10 straight batters before Eric Sogard took him deep to lead off the sixth. He was pulled with two runners on after throwing 85 pitches, and Mark Melancon worked out of the jam.
The Giants extended their streak of first innings without scoring a run to begin a season to 24 games on Tuesday, the second-longest such spell in major league history behind the 28 put up by the 1948 Chicago White Sox. Gerardo Parra was thrown out trying to steal home to end the inning.
Blue Jays: The team announced Tuesday that top prospect Bo Bichette broke a bone in his left hand after being hit by a pitch while batting for Triple-A Buffalo on Monday. The shortstop will visit a hand specialist to determine a course of treatment. ... Montoyo believes RHP Aaron Sanchez will be able to make his scheduled start on Saturday despite the cracked fingernail that forced him out of Sunday's game after four innings. ... LHP Ryan Borucki (left elbow) and RHP John Axford (right elbow) will both be re-evaluated on Friday. ... RHP David Phelps is scheduled to throw his second bullpen session on Saturday as he works his way back from Tommy John surgery last year. ... LHP Clayton Richard (right knee) is continuing his long-toss program and is set to undergo his first bullpen session this weekend.
Giants: LHP Drew Pomeranz (0-2, 4.82 ERA) makes his fifth start of the season and ninth of his career against Toronto. He is 2-1 with a 3.76 ERA in six games at Rogers Centre.
Blue Jays: RHP Clay Buchholtz (0-0, 3.38) will aim for his first win as a Blue Jay. He is 1-0 with a 1.80 ERA in four career starts against San Francisco.
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Belt's homer breaks sign at Rogers Centre
Brandon Belt smashes a solo shot to right field that breaks a sign in the stands.