Charlton fear left-back Lewis Page could be out until October after an injury setback.
Page, 21, injured his hamstring in March, and was expected to return to training in pre-season.
But he needed to have a second operation on his ruptured muscle after slipping on a wet surface in a freak accident.
Charlton head of medical services Alastair Thrush said: “Lewis was entering the final four weeks of his rehabilitation programme, following his initial surgery in March.
“He was due to integrate back into training again when the squad assembled for pre-season.
“He will now have to undergo a further period of rehabilitation with the medical team and it is anticipated that he could return to action in October time.”
MORE: Revealed - How much Peterborough star will cost Charlton
Page has had a tough start to life at the Valley since signing from West Ham in January, playing just eight games.
His extended absence leaves Charlton without any available left-backs after Adam Chicksen’s release and Jay Dasilva’s return to Chelsea.
Page added: “It’s very frustrating for me. I’d put a lot of hard work in with the medical staff over the close season and was looking forward to hitting the ground running in pre-season.
“It was a small slip and I felt a pop in my hamstring again. These things can happen, though, and now I am just concentrating on coming back in the best shape I can.
“While I’m off my feet, I’m using the time to do a lot of extra video analysis work to try and improve the tactical side of my game. Although it is tough at the moment, I’m confident I can return in the best possible condition.”
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here