but they are not similar players, Duffy is unique among our centre backs in that he is better with his head than his feet and that will make us better at corners (attacking and defending). I think he has a role to play in certain circumstances.
The question is who are we going to get in, do we replace with our youngsters e.g. Molumby or get new players in who might be untried at this level. None of the names in your list come as a surprise but I would add Propper . I am not sure why Ali J has not been given more game time to prove his...
If Villa go down who from their team would we take (assuming they have to do a fire sale due to the money they spent). I would be interested in Heaton and John Mcginn though I suspect they might be on better money.