Charlton have revealed that defender Djimi Traore fractured his left leg during the defeat at Chelsea.
Traore has had a troubled start to his Charlton career
The 26-year-old has been given a protective boot as he recovers from the hairline fracture and is set to be absent for several matches.
Wayne Diesel, head of Charlton's medical department, said: "It's only a small fracture, but Djimi has trouble putting weight on it.
"With fractures it's hard to estimate how long they will take to heal."
Traore's injury was the most serious of three sustained by Charlton players in Saturday's 2-1 setback at Stamford Bridge, with both Andy Reid and Souleymane Diawara suffered hamstring injuries.
The former Liverpool defender, Diawara and Reid were all summer signings by new boss Iain Dowie who must now plan without them for Saturday's home match against Portsmouth.
Reid is likely to return before his new team-mates, with Diesel telling club website www.cafc.co.uk: "The soft tissue injuries are quite similar but from the scans it seems that there has been less trauma with Andy.
"The good news is that both players were feeling a lot better on Tuesday, and hopefully they will be moving around more freely by the end of the week."