The above scenario is the only possible four-way tie, and it means all four teams finish with 91 wins (which is the win ceiling for Toronto and Seattle). Each team would choose or receive an A, B, C or D designation. The club with the highest winning percentage in games among the tied clubs chooses first, second-highest chooses second, etc. In this scenario, the Red Sox (24-21 against the others) get first choice, the Blue Jays (22-22) choose second, the Yankees (22-23) choose third and the Mariners (9-11) get the leftover spot.
On Monday, Club A (likely the Red Sox) would host Club B, and Club C (likely the Blue Jays) would host Club D. So for the Yankees, it would come down to a choice of traveling to either Boston or Toronto.
The winners of those two games on Monday would face each other Tuesday in the AL Wild Card Game.