Ac Milan brought him quality players both in midfield and in attack but they failed to do so in the defence. This is the main reason why I can rate their transfer done a one hundred percent. Though, they have players who can thrive until they go get a new defender when the January transfer window comes. I can't say completely where they would end up but best believe, first 4 has got to be their set target if I'm not mistaken. 
The loss to Cremonese showed that they need to improve in the defence since they conceded two goals. However, the club got some defenders like Koni De Winter, Pervis Estupiñán, Zachary Athekame, David Odogu, Davide Bartesaghi, Pierre Kalulu, Davide Calabria and Marco Pellegrino. Since some of them are new to Serie A, they might be getting used to the league slowly. As they keep playing, many of them will improve and the defence will become solid. This international break would be a good time for Massimiliano Allegri to plan well for the next games.