The Yankees need another starting pitcher, both for the season and for the playoffs. They dont want to trade the farm for Halladay, and there isnt a lot out there on the trade market. Wang is looking questionable at best. I know it may sound crazy, and the chances of it happening are a long shot to say the least, but how awesome would it be if Mike Mussina, came back just for one more season(partial), and added a world series ring to his hall of fame case?
Now obviously, there is always the chance he may not be effective, but he was very good last year, and he would be pitching for less than half a season by the time he is ready. He doesnt have to be an ace or even a number 2, just a number 3 type who can keep us in the game for 6 innings.
Of course all this is moot, if he doesnt want to come back, and chances are he doesnt.