Meanwhile Nick Montgomery felt discomfort to his back at Pride Park. Matthew Spring will be out for three to five weeks after he fell over on his ankle. Blackwell has indicated it seems more serious than first thought.
On Spring's incident he said: "He went over on his ankle quite severely which damaged his ligaments, although I'm hopeful that he will be back in the in side three or four weeks."
On the team news as a whole he commented: "We have a couple of niggling injuries to assess on Tuesday before making a decision. Nick Montgomery ended Saturday's game in some discomfort with his back, but you know he is as tough as old boots and he will be soon over it.
"Hopefully, Ugo Ehiogu, who couldn't shake off a groin strain in time for the Derby game, should start training again today although I thought Morgs and Killa did well on Saturday."
In the Coventry camp Guilliame Beuzelin is a doubt. Aron Gunnarsson will be the ideal replacement if Beuzelin can't make it.