De gea, valencia, bailly, jones if fit, blind, pogba, matic, herrera (squad player), martial, rashford (squad player)... not sure on Lukaku. Mkhitaryan and mata are good squad players if used as squad players. Darmian good enough for a squad player at either fullback.
But it definitely depends on the system used. Martial is a much bigger talent then sterling and a better player right now, but sterling is playing consistently in a very high functioning attack. Put martial in that team and he would tear up the league. Rashford less so IMO as he isnt as developed but he'd have a role for sure. Herrera could (and has) perform a similar role to fernandinho as they are similar players. Pogba is quality of course, bailly, jones and even rojo when fit are better then City's center backs imo, valencia is as good a right back as any in the league, blind is good enough at left back in the right system (and no worse then fecking Delph playing there for City).
Lukaku is a question mark for me because he hasnt proven yet that he can play at a high enough level, while he definitely couldnt play in a system like peps or fergies because of his weaknesses, and those 2 systems have always been successful in the league.
Players who aren't good enough for even squad player level IMO are fellaini, smalling, lingard, carrick (too old now) and Shaw. Possibly lindelof too, though early days. Lingard is decent but he isnt a winger who creates, he isnt a pure #10, he doesnt score too many goals.... he just kinda drifts around in a free role, but is mid table level at that. Fellaini needs to be a target man to be at his best, and systems with target men won't win the title. And there has to be better ways to go about comebacks then hoofing it up to one. Smalling is way too limited on the ball for a title winning side, while Shaw doesnt even stick out playing for the youth team. So yeah. A bit of dead wood, but mostly down to system used I think. Also reliant on rashford and martial developing more.