If they have the money, then why don't they sign players!! for the past 3-4 years milan spent the least money on new players when compared to other serie A or european big dogs. Everyone on the planet knows that they don't have enough depth in their squad and still they don't buy players....
Remember Juve when Capello was in charge. After they won the scudetto with Capello, they bought only one big signing, Patrick Vieira. Even though we had the money we didn't waste it on players. Since things were working out for us then, we had no reason to introdce more players into the squad. It's the same with Milan, they are CL winners thus have reason to believe their squad is strong enough, therefore instead of taking risks and buying new players, they paid loads of money to maintain their current players.
This summer all will change. They have the money, they performed badly this year, they will go crazy in the transfer market.
