Burgess Hill Town skipper Will Miles is likely to miss the rest of the season.
The defender dislocated his knee against Kingstonian in the second game of the season and an MRI scan revealed the damage was extensive.
A statement on the club's website said: "The club is devastated to hear the news that after an MRI scan, our captain has ruptured his MCL, ACL and also badly injured his LCL too.
"He now faces a long rehabilitation and will most probably not see him play again this season.
"Everyone at BHTFC and all football fans wish Will a speedy recovery."