A lot of talk the last few days has centered on Cesc and his ability to play the pivot. Against lesser competition, Chelsea relied on a 4-2-3-1 a majority of the season and used Ramires and/or lampard in the pivot for a lot of these games. I do not see Cesc struggling to play the pivot against swansea, Burnley or West Brom.
That said, a lot has been made of how we can go about replicating Luiz' performance against top competition. Lets start with the champions league. Matic will be available to play and he is better as a DM than Luiz. Against a Real Madrid or a PSG though, could fabregas be his partner in a pivot with oscar also on the field? I dont think so. This leaves a problem. If we choose one of Oscar/Fabregas (whether it is a a #10 in a 4-2-3-1 or as an attacking minded box to box mid in a 4-3-3) who else plays with Matic?
In my mind, the dream is still Pogba. If we added Cesc and Pogba, we would play a lot more 4-3-3 and have the same type of dynamic midfield we had during Mourinho's first run with the club. However, what happens if we dont sign anyone else? There has been a lot of speculation that we will sign felipe luis as our LB. Ivanovic is still a very good right back. Where does that leave Azpilicueta? No one could have possibly seen Azpi force out Ashley Cole at LB as a right footed player. Not only did he do just that, but he went on to win players' player of the year. He has a great work rate, he is very good at winning back possession and he is an underated passer. Could he play next to Matic and form a defensive partnership, at least some of the time? I think the answer is yes. Mourinho has shown he will think outside the box and he has shown how highly he thinks of Azpi.
If we dont sign a new midfielder and do end up signing Felipe Luis, I expect to see Azpi deployed as a DM some this season and I think Azpi is a good enough player to thrive in that role.