Ayala spent part of last season on loan at Hull, where he made 12 first team appearances. Hull now want to sign the Spanish defender on a permanent basis but it appears the clubs are miles apart on Ayala's valuation.
"I never rule anything in or out but I would say it's unlikely," admitted Tigers boss Nigel Pearson.
"Ayala is a target and we've put a bid in. The clubs are in discussion and we'll see where it takes us.
"As always the criteria of how you add to your squad is governed by finances."