Ben Reeves will miss the start of the 2018/19 season after picking up an Achilles injury during the first week of pre-season training.
The setback came at Sparrows Lane before the rest of the squad jetted out to Portugal and is likely to keep him sidelined until September.
Reeves said: “I’m gutted and really frustrated. I’d done a lot of work during the summer to try and make sure that I was ready for the start of pre-season. I was determined to come back in the best possible condition and to pick up an injury a couple of days into it is so gutting.
“Hopefully I can get myself back out onto the pitch as quickly as possible and I’ll be doing everything I can to make sure that is the case.”
Charlton’s Head of Medical Services Alastair Thrush said: “Ben has sustained an acute small tear in his left Achilles tendon, which requires a short period of immobilisation in a boot for four weeks.
“Thereafter, he will require a further period of rehabilitation and fitness work to bring him to a level where he would have been if he had followed the normal pre-season programme with the squad.
“All being well, it is anticipated that he will be back in full training around the beginning of September.”
Thrush also provided the latest on Billy Clarke. He added: “Billy is continuing his rehabilitation from his ACL surgery and is back outside running and completing ballwork drills. It is anticipated that he will start to integrate back into full training from the middle of September.”
The pair have been at Sparrows Lane this week and got behind the Addicks participation at Pride in London on Saturday.