OAKLAND, Calif. -- When Toronto Blue Jays third baseman Josh Donaldson came to the plate in the top of the 10th inning on Wednesday against the Oakland Athletics, the score was tied 4-4 with no outs and Kevin Pillar on first base.

Four pitches later, Donaldson launched Frankie Montas' 98 mph fastball over the left-center field fence for a two-run homer against his former team, and the Blue Jays held on for a 7-5 victory at Oakland Coliseum.

The Blue Jays expected nothing less from Donaldson, who has made a habit of late-game heroics.

"The game's on the line in a big situation, we always expect that," said Blue Jays first baseman Justin Smoak, who hit his 16th and 17th home runs of the season. "He's done it so many times."

Smoak hit two solo home runs -- one in the second inning and one in the 10th -- and Pillar hit a three-run homer in the second for Toronto, which won the series finale to avoid a three-game sweep.

Leading off the 10th, Pillar fell behind in the count 0-2, but Montas drilled him with a pitch. Then Donaldson hit Montas' 1-2 pitch for his seventh home run of the season, this one coming against the team that traded him to Toronto after the 2014 season.

Donaldson said there's still something special about coming up big at the Coliseum, where his major-league career began.

"I was able to do that a few times when I played here too," said Donaldson, who was the American League's MVP in 2015. "So it was nice to kind of be able to come back and hit one in a timely situation."

Blue Jays manager John Gibbons wasn't surprised when Donaldson went deep.

"Once again, Josh does something big when we need it," Gibbons said. "That's what MVPs do. He's good, but he knows he's good. He'll tell you he's good. That's what star players do."

Two batters later, Smoak hit an opposite-field homer to right-center field off Montas (1-1), who has allowed nine home runs this season.

"He left some balls up in the zone," A's manager Bob Melvin said of Montas. "The second one was a breaking ball. May have sped him up. You know he's got a good fastball. He's proud of the heater, but you know when you get it into the middle of the plate at the big league level against good hitters they're going to turn it around, as you saw."

Blue Jays right-hander Roberto Osuna gave up a run in the bottom of the 10th but got his 14th save of the season. Rajai Davis doubled with two outs and scored on Matt Joyce's single before Osuna struck out Jed Lowrie.

Toronto's Danny Barnes pitched perfect sixth and seventh innings with three strikeouts in relief of Francisco Liriano. Joe Smith pitched a perfect eighth with two strikeouts, and Ryan Tepera (4-1) a perfect ninth with one strikeout.

"They've been on a nice little roll," Gibbons said of his bullpen.

Rajai Davis went 4-for-5 with a triple and two doubles and scored four runs for the A's. He matched his career high for hits. Trevor Plouffe hit a solo home run, and Khris Davis had a double and two RBIs in four at-bats.

"I think I just was able to simplify everything, not do too much and just use my hands," Rajai Davis said.

Liriano allowed four runs (three earned) and six hits in five innings in a no-decision. Making his second start since a stint on the disabled list for right shoulder inflammation, Liriano struck out five, walked one and threw 92 pitches.

A's right-hander Jharel Cotton gave up four runs and four hits in six innings, striking out four and walking four. He blanked the Blue Jays in five of his six innings but gave up four runs and two homers in the second inning. Cotton made his third start since being recalled from Triple-A Nashville on May 27.

The A's took a 1-0 lead in the first when Rajai Davis hit a leadoff double to center field, moved to third on wild pitch and scored on Khris Davis' double.

Toronto answered with four runs in the second. Smoak, who had his first two-homer game of the season, led off with an opposite-field shot to left-center field.

"I can't describe it," Gibbons said of the season Smoak is having. "Nobody's ever seen him this good with us. I can't say enough good things about this guy."

Cotton struck out the next two batters he faced, but then walked left fielder Chris Coghlan and gave up a single to Ryan Goins. Pillar followed with a three-run shot to left center, his eighth homer of the season, making it 4-1.

Oakland cut Toronto's lead to 4-2 with an unearned run in the third. Plouffe made it 4-3 in the fourth with a leadoff home run that snapped his career-high 0-for-25 streak.

In the fifth, Rajai Davis led off with a triple to deep left field that Coghlan couldn't grab and scored on Pinder's sacrifice fly to make it 4-4.

Five innings later, Donaldson got the lead back for Toronto with one swing.

"I was able to get a fastball over the heart of the plate and get enough on it to get it out," Donaldson said.

NOTES: Oakland 1B Yonder Alonso, who has a career-high 16 home runs, was out of the starting lineup but pinch hit in the 10th and remained in the game. ... A's RF Matt Joyce (strained right quad), who missed Tuesday's game, pinch hit in the eighth inning and remained in the game in right field. ... Blue Jays C Russell Martin returned to the lineup after getting a day off Tuesday.