Beside the recruitments on August 2010 the January transfer windows gave big contributions for the scudetto journey:
1. The recruitment of Cassano
Cassano made 4 goals and 6 assists. So that makes him contributed 8 points for Milan since his arrival.
2. The recruitment of Urby Emanuelson
Urby turned to be versatile player. he can be put in any position except for front line. he could be very useful if teams need the player who should be watch to keep the balance in the game.
3. The recruitment of Mark Van Bommel
Even I was cursed the management at the first when I read that they will be signing Van Bommel (I said: OMG what an old crack player, why Milan always have such this habbit ?
) but his contributed appareantly very crutial considering so many names that got injured during the journey before end of season.
These recruitments could be alternatives for Allegri to put the answer for the absence of many key players. For example the absence of Pato and Ibra could be replaced by the duet of Cassano and Robinho. and when Pirlo and Max absence for a very long time Van Bommel keep the wheel gone around.
beside those 3 names Milan also got Didac Villa and Nicola Legrottaglie.
So I think the cleaverness of recruitment from management is one of the key why Milan is the most consistence club in Italy and ended with scudetto even when the season haven't ended yet and left their rivals far far far away