The solid second baseman, who is a contact hitter on a free-swinging team, was out for more than a month with a separated left shoulder.
"It feels really good to be back and to help the team win," Polanco said. "These are important games because we're trying to win the division and get the home-field advantage."
Detroit (95-62) maintained its one-game lead over the Minnesota Twins, who beat Kansas City 3-2. The Tigers in essence have a two-game lead because they won the season series against Minnesota and would win the tiebreaker if they finish with the same record Sunday.
"We're going to have to win more games because (the Twins) are winning, too, so we have to keep it going," said Todd Jones, who pitched the ninth for his 37th save.
The Tigers, who have won eight of 11 after a prolonged slump, remained tied with the Yankees, who beat Baltimore 5-4, for the AL's best record (95-62). Detroit clinched a spot in the playoffs -- for the first time in 19 years -- on Sunday.
Polanco hit a two-run, two-out single in the second inning and his squeeze bunt in the sixth gave the Tigers a 4-1 lead. He is hitting .394 with runners in scoring position.
"He's a versatile player," Detroit manager Jim Leyland said. "He got a big hit and got the squeeze down."
Leyland acknowledged he does not like squeeze bunts, but the savvy manager wanted to give scouts something unexpected to jot down in their notebooks.
"This time of year, we're being watched by Oakland, the Yankees, Minnesota and the National League," he said. "So anything you can throw out there that they have to put down to be aware of is to your advantage."
The Blue Jays pulled within 4-3 in the seventh on Frank Catalanotto's single and Alex Rios' run on a passed ball.
"There are not going to be any easy games, but it's nice to know you're in (the playoffs) for sure," Leyland said.
Bonderman (14-8) gave up an unearned run, three hits and three walks while striking out four, becoming the first Detroit pitcher since Jack Morris in 1987 to reach 200 strikeouts.
He won his third straight start after going 0-4 in his previous nine.
"Hopefully, that gives him some confidence because we're going to need him in the playoffs," Jones said.
Leyland said he might rest Bonderman on Sunday in the regular-season finale to get him ready for the postseason. Leyland said he plans to skip Justin Verlander's start Saturday to give him a break and set up his rotation.
Rookies Andrew Miller and Joel Zumaya combined to pitch the seventh with Miller giving up a run on a walk and Zumaya giving up an unearned run on the passed ball. Fernando Rodney pitched the eighth, giving up a walk and single.
The Blue Jays (83-74) had won eight of 11, improving their hopes of finishing higher than third in the AL East for the first time since winning the World Series in 1992-93.
With Toronto's loss and Boston's win, the Red Sox moved a half-game ahead of the Blue Jays for second in the division.
"We've got a battle for the next five days with Boston," Toronto manager John Gibbons said. "Being in second place was short-lived, obviously, and we hated to relinquish that. Boston's tough at home and playing two teams they've beaten up this year, but we've got five days to get it back from them."
Dustin McGowan (1-2) gave up two runs -- both unearned -- two hits and a walk over two innings in his second start of the season. McGowan, who has 12 relief appearances, made his previous start on July 29.
- Detroit OF Magglio Ordonez was replaced in the top of the third inning because of spasms in his lower back. "I think he'll be fine," Leyland said.
- Detroit hopes OF Marcus Thames can play Wednesday. "He's sick with a fever and a sore throat," Leyland said.
- Toronto OF Reed Johnson (leg) was out of the lineup, but was used as a pinch hitter in the seventh and struck out.
- Bonderman has pitched six innings in each of his last three starts.