The playoff would be held Monday, Oct. 7 at Fenway Park, the league said.
Toronto won the right to make the call of the flip, which was held at AL president Bobby Brown's office.
The league playoffs begin Oct. 8 in the city of the West Division champion.
In past seasons, division champions chose the same 25-man postseason roster for the playoffs and World Series. The Pirates want to structure the roster to the opponent, which could mean roster moves between the playoffs and World Series.
Such moves usually are allowed only in the case of injuries, so general manager Larry Doughty has asked NL president Bill White to determine if the Pirates can make postseason moves involving the 30 eligible players.
"He's promised me a ruling," Doughty said. "He said it's a unique idea to think in terms of doing something like that. He said no team had ever discussed it before, altering the roster to the opponent . . . and he said he'd check into it."