If the teams finish in a dead heat after Sunday, a one-game playoff to determine the division champion will be played at Yankee Stadium on Monday.
Both teams are also still very much alive for the wild card. The Yankees also lead Cleveland by one game. The Indians will conclude the regular season with three against the AL Central champion Chicago White Sox.
If the Red Sox, Yankees and Indians finish tied, New York will play Boston on Monday, with the loser heading to Cleveland for a one-game playoff to determine the wild card.
I think this means that the Red Sox have to win the three games to play for the division championship on Monday. The rest is still slightly confusing.
In another race, the Phillies have not quite stopped playing baseball yet. If they win their last three games against Washington, and Houston loses three to the Cubs, then the Phillies make it as the National League Wild Card. It seems like they are in a precarious position and shouldn't have let it get this far, but they are not out yet.
Although it does seem like you have to be a math professor to understand these combinations, I think that I can put it more sipmply. In summary - cheer for the Red Sox to beat the Yankees, as always. Cheer for Philadelphia to win their games as always, and cheer for the Cubs to win their games, as always. It isn't really that hard to remember.