Hulse, 26, a former Crewe and West Bromwich Albion striker, scored 14 goals last season for Leeds and fits into that category.
Blackwell has already spoken out about a potential move to Bramall Lane for defender Matthew Kilgallon, with him saying: "Players like Killa are the future of this football club. We wouldn't want him to go anywhere. I hope this is the end of the matter now."