BOSTON -- The Boston Red Sox would like to get the AL East wrapped up quickly so they can start resting some banged-up players.
Josh Donaldson homered and drove in three runs, powering the Toronto Blue Jays past the first-place Red Sox 6-4 on Monday night.
Boston's six-game winning streak was snapped and its magic number to clinch a second straight division title remained at three. The Red Sox lead the second-place New York Yankees, who beat Kansas City earlier in the day, by four games with six remaining.
But the most important thing for the Red Sox was the loss of two key players to injuries. For how long? They don't know yet.
"We'll get it looked at further tomorrow," Betts said. "I'm not really that concerned. Everything will be fine. Couple of days ago, I took a swing and felt it. It's just that point of the season."
Nunez sparked Boston's offense after he was acquired from San Francisco in late July. The utility infielder is batting .321 with eight homers and 27 RBIs in 38 games with the Red Sox.
"Day to day at this point," manager John Farrell said. "I don't have a clear indication of when he'd be next available."
Red Sox lefty Drew Pomeranz (16-6) had his shortest start of the season, giving up five runs and seven hits in two innings. He had lost only once in his last 18 outings, holding opponents to three runs or fewer in 16 of those games.
Betts drove in two runs, going over the 100-RBI mark for the second consecutive season. Andrew Benintendi had a pinch-hit solo homer.
Boston's loss assured AL Central champion Cleveland of home-field advantage in a best-of-five Division Series that will begin Oct. 5. The Indians' opponent has not been determined yet.
Ryan Goins hit a solo homer and Teoscar Hernandez had a two-run double for the Blue Jays. Brett Anderson (2-2) allowed three runs in five innings.
It was Donaldson's 22nd homer since the All-Star break, most in the AL.
"I think what happened is he's healthy now," Blue Jays manager John Gibbons said. "At the beginning of the season he lost six weeks, seven weeks. I don't know what it was. But to be where he's at, he shows what kind of hitter he is, what kind of player."
Roberto Osuna got three outs for his 38th save.
Toronto slugger Jose Bautista was ejected by plate umpire Chad Fairchild after getting called out on strikes.
Coming off an 8-1 road trip that helped them maintain control of the AL East, the Red Sox fell into an early hole.
The Blue Jays chased Pomeranz with four runs in the second to take a 5-2 lead when Hernandez and Donaldson each hit a two-run double.
"My velocity has dipped a few times but it's come right back when I need it," Pomeranz said. "I really didn't have a chance to get settled in with the short outing."
Donaldson homered about a third of the way up a light stanchion in left-center in the first.
Red Sox: Nunez fouled off a pitch his second time up and went to the ground in pain. He finished the at-bat with a lineout to third, but barely got out of the box and was unable to put much weight on his knee. ... Betts grabbed his left hand in pain after a bloop single and pointed at it while talking with a trainer.
The 24-year-old Betts has 101 RBIs and 98 runs scored this season. Last year, the right fielder drove in 113 and scored 122. The only other Red Sox player with multiple 100/100 seasons before turning 25 was Hall of Famer Ted Williams from 1939-42. "It's pretty cool anytime your name can be amongst him," Betts said.
Blue Jays: LHP J.A. Happ (9-11, 3.64 ERA) is set to pitch the second game of the series Tuesday night. He lost his last start Thursday after winning the previous three.