I'd take issue that MDS isn't needed. The depth there still isn't great at all and Rodriguez has a lot to prove going forward. I like Calabria's potential a lot but he's still very raw.
Locatelli's coming off his first full season of Serie A footie. And showing well. Why you want another player in his way? I'm all for Montolivo being slowly phased out as he was last year. But you add Biglia and he'd be the opposite of that vet. and demand games. And when you've got some very versatile midfielders like Bortolacci who can quite competently fit in there if needed, I personally can't agree that you need another vet. who'll start.
I just don't see him being a significant upgrade for a team that's far from in a 'win now, one vet. away' mode and more so someone that set's back a developing player who is the future in the role.
Conti has already come in as a RB. Abate might be gone, but most likely I feel Calabria will get a loan. With MDS Milan have 4 right backs at this moment. As for LB there is Antonelli, Rodriguez and Vangioni who is most likely back off to River.
As mentioned by ToD Bertolacci is off and Montolivo might also be off. That leaves big gap in midfield even with Kessie signing. Bonaventura, Biglia and Kessie would be starting, but there is lot of games for Locatelli to play and develop.