The Blades are already without fellow forwards Jamie Ward, Darius Henderson (both hamstring) and Ched Evans (collarbone) and Blackwell is fast running out of partners for Richard Cresswell.
Skipper Chris Morgan has served his two-match ban, but Blackwell is still without midfielder Lee Williamson (hamstring), on-loan Fulham full-back Toni Kallio (calf) and long-term absentees Gary Naysmith, Ryan France (both knee) and Derek Geary (ankle).
Blackwell was forced to field five on-loan players last Saturday at Doncaster and the latest to arrive, goalkeeper Steve Simonsen, will start his second match following the return to Blackburn of Mark Bunn.
Source: Team Talk
Source: Team Talk