Imps manager Chris Sutton told BBC Lincolnshire: "It is a big blow. Paul has done exceptionally well - he has been our best player in recent weeks.
"It's unbelievable that we have lost so many centre-halves this season."
The Imps face their final three games without four players who have played at centre-half this campaign - Paul Green, Moses Swaibu, Ian Pearce and Adam Watts.
Source: BBC Sport
Source: BBC Sport