TORONTO -- The Toronto Blue Jays thought they would be hitting against Oakland Athletics ace Sonny Gray on Thursday.

But the right-hander developed back spasms Wednesday night and could not pitch. They faced right-hander Jesse Chavez instead of Gray, who leads the American League with a 2.06 ERA.

Chavez pitched well but was done in by a four-run second inning keyed by Ryan Goins' three-run homer, and Blue Jays left-hander Mark Buehrle pitched into the eighth.

It was just enough for the Blue Jays, who completed a three-game sweep of the Athletics with a 4-2 victory to extend their winning streak to 11 games.

"It was one of those games," Blue Jays manager John Gibbons said. "We were fortunate to get that big inning and Jesse Chavez was really, really good. Good win."

Athletics manager Bob Melvin said, "Really one pitch, he was trying to go up and in to Goins and left it out over the plate where he got the barrel on it. Other than that, he was great. Pitched well against a hot lineup."

The Blue Jays (64-52) entered Thursday with a half-game lead over the second-place New York Yankees in the American League East. The 11-game win streak equals a franchise high, most recently accomplished June 2-14.

Chavez (6-12) allowed all four runs in the second. Catcher Dioner Navarro, first baseman Justin Smoak and center fielder Kevin Pillar hit successive one-out singles to produce one run.

Goins, who played shortstop with Troy Tulowitzki getting the day off, hit his fourth homer of the season to score three more for a 4-0 lead.

"Just one pitch," Chavez said. "Trying to go up and in. He just got the hands out and beat me to it. I thought it was a good pitch and it as out of the zone. Here, if you get the ball up, it's got a chance to go. He got it up and it went."

Goins, who batted eighth, said, "The big part of this lineup is going to be one through five-six-seven. So us guys at the bottom, we're just trying to have a good at-bat and turn it over to those guys. So they're going to be the guys who carry us."

Chavez allowed six hits and no walks while striking out nine in six innings before left-hander Drew Pomeranz took over in the seventh.

"I think he went in with the right attitude," Athletics catcher Josh Phegley said. "I don't think you want to be ambushed like that and be thrown in there. It was tough not to see Sonny in there. We've counted on him all year and he's been there for us all year. (Chavez) didn't use it as an excuse.

"He threw the ball great. I told him take one pitch away from there and it's a great outing and we win the game."

Buehrle (13-5) allowed seven hits, two walks and two runs while striking out two for his fourth win in a row.

The left-hander did not retire a batter in the eighth. Shortstop Marcus Semien led off with a single. Pillar made a diving attempt on a hit by center fielder Billy Burns, but it went for a run-scoring triple.

Right-hander Aaron Sanchez replaced Buehrle and retired first baseman Mark Canha on a grounder to second as Burns scored from third to trim the deficit to 4-2.

Smoak made a superb grab on a grounder by second baseman Brett Lawrie for the second out, and third baseman Danny Valencia struck out to end the inning.

Right-hander Roberto Osuna pitched the ninth for his 12th save of the season. After designated hitter Billy Butler flied out to the wall in right field for the second out, right fielder Josh Reddick doubled to right. But left fielder Coco Crisp lined out to right to end the game.

A key part of the game came in the top of the first when the Athletics loaded the bases with no outs and could not score.

Third baseman Danny Valencia bounced back to Buehrle to start a home-to-first double play and Phegley grounded out.

"For me, bases loaded, nobody out, it's usually a guaranteed of at least a run or two because I don't strike guys out," Buehrle said. "But threw a curveball to Valencia and he luckily grounded back to me."

NOTES: Oakland RHP Sonny Gray (back spasms) was scratched from his scheduled start after the condition developed Wednesday night. RHP Jesse Chavez, who was scheduled to start Friday in Baltimore, took the start Thursday. Manager Bob Melvin was not certain when Gray might return or who might start Friday. ... Toronto DH/1B Edwin Encarnacion (sore left middle finger) missed his fourth straight game but was available to pinch hit. He could return Friday for the opener of a three-game series against the New York Yankees. ... The Blue Jays will start LHP David Price (11-4, 2.35 ERA) on Friday at Rogers Centre against Yankees RHP Ivan Nova (4-4, 3.52). ... The Athletics open a four-game series at Baltimore on Friday and will be facing Orioles RHP Ubaldo Jimenez (9-7, 3.79). ... The announced attendance of 46,902 was the seventh sellout at Rogers Centre this season.