Although I agree about form with Dier, he hasn't hit his standards of the last few seasons this year, he has still been pretty good, and is easily one of our best players.
Can't understand why some fans would want to sell him, he offers us so much versatility and flexibility tactically in a game. He can play DM, drop in to a back 3, or be the CB in a 4 man defence.
Simply put, to replace Dier we would need to sign 2 players (a CB and a CM) as any player that has the ability, versatility and flexibility he has is going to cost well over £50million - if there are any of them about?
We are better off keeping Dier, making him a CB if Toby goes and letting him develop into a great ball playing CB.