Question is why did you want him before?
Without the perfect pressing/synched up movement system in Atalanta, he, like many of their players, will be found out for what they are outside it. Not to mention he plays as wingback there who has coverage by 3 CBs and and a close by DM, basically gets to attack as much as he wants well drilled approach.
Put him in 4 man defense in average looking set up and you find out individually he is another Abate.
That Milan are paying 28m for