Blackwell said on the club's official website: "Any loan signings will be to make sure I have a squad strong enough to get us through the play-offs if need be.
"If there was any chance of Richard Cresswell being fit I wouldn't even go down that route but it isn't going to happen so I have got to have someone in mind, but it has to be someone who can do the job and not just fill out a team sheet."
Sunderland striker Andy Gray seems to be the front-runner for a move after a disappointing Premiership season at Sunderland.
The former Leeds striker has attracted plenty of interest from Championship clubs, with Derby County and Burnley also previously interested.
Gray was left out of the Sunderland reserves squad earlier this week (the game was eventually called off), as a precaution, fuelling rumours of a move.