Sharpe's problems began after only two days of pre-season training last July.
He recovered from his injury in time to join the first team for pre-season training before the beginning of 2011-12.
Stewart resigned the position at season's end, then went missing for pre-season training.
He missed all of the 2012-13 pre-season training with a calf injury.
However he failed to turn up at the club for pre-season training.
He put his poor form down to him missing pre-season training with injury problems.
He was persuaded to return, but told to stay away until pre-season training began in June 2008.
During 2010/2011 pre-season training he was called for the first team.
Niort returned from the summer break to pre-season training on 25 June.
Then, in the middle of pre-season training the knee got very painful,' said the 22-year old.