I'm kidding around, but Ebbets Field was a few blocks from 770. You could hear the crowd from there!
Also: http://www.chabad.org/library/article_cdo/aid/95881/jewish/Fans-and-Players.htm
I know you are kidding. Worry not.
If memory serves correctly, the Rebbe once asked Leibel Groner, "why do you look so down, the Dodgers won?" To which he replied, "the Groners are Yankee fans."
I believe on another occasion, the Rebbe asked Leibel, "nu, vos machen dein Yankees?"
Which is telling, because I'm pretty sure Rabbi Groner didn't follow any sport team, but Rabbi Krinsky was a admitted Red Sox fan. The Rebbe clearly didn't want to bring them up.
But the Rebbe must have been a Yankee fan, as the Yankees are truth. At the core of Chabad chassidus is the idea:
"איך וויל וויל זע גאָרניסט, איך וויל ניט דיין גן-עדן, איך וויל ניט דיין עולם-הבא, איך וויל מער ניט אַז דיך אַליין"
As portrayed in 8th Day's "Tatenyu", Yaakov Halevi's quest for #truth finds him "still a big fan of the Yankees".