Charlton have revealed that defender Djimi Traore fractured his left leg during the defeat at Chelsea.
The former Liverpool player, 26, has been given a protective boot as he recovers from the hairline fracture and is set to be absent from Charlton's first team for several matches.
His 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.
Traore's injury has caused the most concern, and Wayne Diesel, who heads Charlton's medical department, said: 'It's only a small fracture, but unfortunately it's enough that Djimi has trouble putting weight on it.
'With fractures it's hard to estimate how long they will take to heal because there is little you can do to encourage the healing; you have to rely on the natural healing process.'
Traore, 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.'