The striker had to be stretched off the pitch just 19 minutes into the mid-season friendly against Aston Villa after colliding with Ezri Konsa.
Broja screamed in pain and clutched his right knee, and play was stopped for a considerable amount of time as the Albanian was assessed by medical staff and then replaced.
Asked for an update after the game, which Chelsea lost 1-0 in Abu Dhabi, Potter admitted the initial prediction “didn’t look positive”.
“It was an unfortunate action, I think he made up for it with their player and the ground,” Potter told Chelsea’s official website.
“It doesn’t look positive at the moment, but it’s too early to tell. Fingers crossed, but it’s embarrassing.”
Chelsea are next in the Premier League on December 27 against Bournemouth.