Generally agree about the CBs. Evans will be excellent with a world class CB alongside him, but he has fairly fundamental weaknesses that mean he can be exposed too easily. A world class CB can be sluggish as long as he's dominant in the air, Evans isn't and that's holding him back, even if the mental side of his game is top class. He's a bit like Rio 5 years ago but without the pace. You get the sense that the standard of our defending doesn't really depend on Evans, he'll be excellent in a good defence and poor in a weak one, instead of setting the tone for the quality of defending like the best CBs do. Still a very good player of course, I imagine him and Vidic will be a fairly regular partnership for the next couple of years.
Smalling certainly has loads of talent but he's got too many mistakes in him and that's stopping him being a first team regular. Assuming they get ironed out with experience he'll be an excellent player though, when he gets towards his late-twenties there's nothing to stop him being world class and talked about in the same breath as the best in Europe. Incredible pace, solid in the air and seems to understand the game like a man 5 years older. Can get outmuscled when isolated and is still a bit rash but hopefully that'll sort itself out as he ages.
Jones is quite a bit further back in terms of his development so we'll have to wait and see, needs time at CB but it's difficult to give him that. Looks like he'd have been best staying at Blackburn for a couple of seasons but that wasn't really an option with other clubs snooping around. The adventure that made him so exciting in his first few months at us has been largely coached out of him, and while he has still shown glimpses of talent they've been predominantly from full back. Thing with him is that he should be looking (even more than Smalling) to develop into a physically dominating CB, you can see that much just from his build, he'll be a tank in a few years. Hopefully the fitness issues are a result of gradually growing into his body. But at the moment he's still a 20 year old kid, and when you think of the top class imposing CBs across Europe today they were nowhere at 20, certainly not playing regularly at CB for a side competing for the title in a top league year in year out. We shouldn't expect Jones to be any different, but give him time and handle his development well and like Smalling he's got the potential to be up there with the very best, even if he's further away at the moment.