baseball or physics?

Anyone who knows me knows that I inherited my love of baseball from my dad. But much to his dismay, I did not inherit his love for the Yankees, and instead chose to go toward the light. So...this is a big weekend. And this is his explanation of it all, which made my brain hurt:

If the Yankees and Red Sox end up tied, the Yankees win the division, because they will have won the season series 10-9.

The only way there is a Yankee-Red Sox playoff game Monday is if the Yankees, Red Sox, and the Indians are all tied. That can only happen if the Red Sox and Yankees split the final two games, and the Indians win their last two games.

so....

If the Red Sox win Saturday AND Sunday, they win.
If the Yankees win Saturday OR Sunday, they win.

The only exception is if the Red Sox and Yankees each win 1, and Cleveland wins 2, leading to a Red Sox-Yankee playoff Monday.