Mansfield Town striker Liam Hearn has been ruled out until after Christmas.
Scans have revealed that Hearn tore cartilage in the incident which forced him came off injured in the Capital Cup defeat against Sheffield United.
The news is a major blow for both club and player and adds to the growing injury problems at the One Call stadium.
Cox is already without the suspended Matt Rhead and the injured Ollie Palmer.
Hearn spent much of the last two seasons on the treatment table with cruciate knee ligament trouble and a ruptured Achilles injuries,
He then had his Grimsby contract cancelled by mutual consent after he asked to leave the club following a series of injuries that meant he made only 15 appearances during the 2013/14 season.