Courtenay Dempsey's AFL season could be over with the Essendon defender suffering a tear to his hamstring tendon in the loss to Collingwood.
It is another significant on-field blow to the Bombers, who are coming off big losses to Hawthorn and Collingwood.
Essendon are also sweating on what the AFL decide to do over the club's supplements scandal, amid speculation they could be stripped of this season's premiership points.
The Bombers are fifth, dropping out of the top four with Sunday's 79-point loss to the Magpies.
Dempsey was subbed out of the game in the first quarter when he hurt his left hamstring.
It is unclear whether the speedy Bombers half-back will need surgery.
"We sent him for a scan to nail exactly what it is and, unfortunately, we got what was probably the worst result we could have had," Essendon football manager Steve Alessio told the club website.
"He has got a tear in his hamstring tendon and, unfortunately, that will mean he is going to be out for at least four weeks.
"We are just going to have to go really conservatively with Courtenay and see how he comes up."
