Yeah, his form recently hasn't been as good granted but 2 STHs I know(glory hunting wankers) told me Smalling has been very good when you consider he's not had a solid consistent partner all season & he's had to play a lot with Blind, who isn't a centre half and has been on the receiving end of...
Smalling has had a largely superb season, without him and De Gea Man united would be God knows where. Apart from him I agree though options look limited but I don't think say Cahill and Smalling is a bad central pairing