This is the problem though. People will say, "Player X became top class when people didn't think he would, so Player Y will", even if there's not the evidence to suggest it will happen. People used to say Anderson was bound to become a top player for example, because Xavi had been a late bloomer. Of course, Evans has already done much better than Anderson ever did and he's a respected player here, but he's not top class. He's coming on 27 - there's not a lot to suggest he's going to be good enough to lead our defence as a world class player, and that's what we should be looking for.
Does that mean we need to sell Evans? No. In fact, I want us to keep him and I think he has an important place in this squad, but if you offered me a top class defender to start ahead of him? I'd take it, and we'd be a bit daft not to.