According to startribune.com:

If the Yankees and Red Sox finish tied, with better records than the Indians: New York and Boston make the playoffs, the Indians are out. Yankees win the AL East because they have the better record vs. Boston.

Interesting. So, the Yankees and Red Sox can be tied and NOT have to play a one game playoff. Of course, counting on the Indians losing isn't a good idea. But, theoretically, we could clinch today. Whew, boy...

Via Steve Lombardi.