Newcastle striker Alan Shearer will have a scan on his knee on Thursday to discover if his playing career is over.
Shearer has netted 206 goals in his Newcastle career
Shearer, scheduled to play three more games before retiring at the end of the season, limped off in the 71st minute of Monday's 4-1 win over Sunderland.
"I will just have to wait and see what the scan says," said the 35-year-old.
"It does not look good. They think there might be a tear in the medial ligament and if that is the case then that will be it for me I am afraid."
Shearer's final game was set up to be the home match against Chelsea on Sunday 7 May and the former England captain said he did not want to finish his career early.
"I will be bitterly disappointed if it is the end because there are three huge games left for us," he added.
"We are sitting in seventh place now, which might get us into Europe and after what has been a tough season that would be a great achievement for everyone.
"I wanted to go the full distance, yes, but if I have to finish, then it's not a bad way to finish, coming to your local enemies and scoring a goal that has helped us get a 4-1 win."
Shearer did not attach any blame to Sunderland's Julio Arca who along with Tommy Miller challenged Shearer to leave him injured.
"To be fair, the Sunderland lad just fell on top of me," said Newcastle's record striker.
"He fell on the outside of my knee and that puts pressure on the inside, and something has given in there.
"The knee is very sore and to be honest, it is not looking good at the
Magpies boss Glenn Roeder has not given up hope that Shearer will play again but feels that if the win over the Black Cats proves to be his final appearance then it would be an appropriate farewell.
"We are not at that stage yet," said Roeder. "You can talk about that maybe in a week's time or four or five days' time if it turns out that is the case.
"But I will remain positive there is a chance we will still get him back on the pitch, maybe in the very last game of the season.
"If we don't, I suppose his memory of scoring then what would be his last goal would be a very, very happy one for different reasons."
Newcastle chairman Freddy Shepherd also refused to write off Shearer's chances of playing again - and backed him to retain his links with the club in the future.
Shepherd told BBC Radio Five Live: "It is not very hopeful but you never say never with Alan Shearer.
"I am sure he will be looking at a coaching capacity with Newcastle in the future.
"I have said it before many times that he will not cut connections with Newcastle. He will stay associated with the club in some way, whether it be as turnstile operator, ambassador or whatever.
"As he has said himself he is not interested in the manager's job here. He wants a rest and that is what he is going to do."
Shearer has scored 206 goals in 404 appearances for Newcastle since he arrived at the club for £15m from Blackburn in the summer of 1996.
He netted a total of 379 goals in 733 appearances - in a career encompassing spells at Southampton, Blackburn and Newcastle.
He also scored 30 goals in 63 appearances for England.