Blackwell and Warnock want Birmingham keeper Ian Bennett and both manager's are after Blackburn's Craig Short and Watford striker Heidur Helguson.
Leeds, Blackburn, Wigan and Sunderland are also interested in signing 31-year-old Steve Watson, who is expected to leave Everton on a free transfer.
Blackwell, meanwhile, has admitted that he wants a fee for Julian Joachim. The former Aston Villa, Coventry and Leicester striker is wanted by Walsall but Leeds have made it clear that the player has not been freed and that any club interested must be expected to pay off his contract.