David Larmour is expected to undergo a scan later today to ascertain the full extent of the damage to his knee.
The Crusaders striker left Seaview on crutches after their 4-1 defeat to Cliftonville 10 days ago, following his substitution in the first-half of that game.
After an appointment with a consultant last Friday, Larmour will now have the knee fully checked out before a full diagnosis is given.
"I still can't straighten my leg fully and it is still quite sore," said Larmour.
"The consultant wanted to get the scan done as quickly as possible and this is about as early as it could have been done after I saw him last Friday.
"Nothing can be determined from the outside, so he needs to have a full examination before knowing the full extent of the damage."
Larmour is definitely out of tonight's County Antrim Shield tie with local rivals Brantwood at Seaview and could be out for a number of months.
He underwent surgery to repair his cruciate ligament some six years ago while at Linfield and there are fears that there may be a repeat of that injury.
" The knee feels very different this time," he said.
"Last time I could walk, but now I need crutches. Fingers crossed it's not as serious.
"It was a completely innocuous injury. I tried to get my toe to the ball to stop a shot and as I did the player who was trying to shoot hit the back of my leg. It was just the kind of challenge you make in every match."