Easily tier two for me. He is probably the best on the ball of all that lot, his calmness on the ball and use of it is probably the best I've seen at united, controversial I know but I think he is.Worth 40-50m to me. Nothing special to be honest, but he is not bad.
If compare to our other CB in the past:
Tier 1: Stam, Vidic, Rio
Tier 2: Bruce, Pallister
Tier 3: Johnson, Berg, Maguire, Brown, Smalling, Evans
Tier 4:, Lindelof, Blind, Jones, Rojo, Bailly
But if he can show up more in couple more years, organise our defence line well, maybe he can be up there with Bruce and Pallister one day. Will have to see.
Re OP, worth it and wouldn't sell him for that.