I always get some good info from Olney's blog, including this one:
More fun with Yankee misery!
The Yankees' deficit in the division race is 14.5 games. Only one team has won a division or league with a deficit of greater than 14 games -- the 1914 Boston Braves.
The Yankees' deficit in the wildcard is 8.5 games. Only four wildcard winners have overcome greater deficits than that -- the '95 Yankees (who were once nine games out), the 2001 Athletics (once 10.5 games out), the 2003 Marlins (11.5 games out), and the 2005 Astros (11.5 games out).
Only two other times have the Yankees had a larger deficit in May -- 1984: In the year in which the Tigers started 35-5, the Yankees fell 17.5 games out in May. 1913: the Yankees were as much as 18.5 games out in May.