The analysis I've read suggests market feeling is they have taken their eyes off the ball with their main operation and haven't benefitted particularly from the trends in athleisure and super expensive trainers the way JD have. There isn't an awful lot of confidence in Ashley's 'buy up failed high street chains' strategy either. In particular his lost investment in Debenhams is regarded by some as a mixture of cockiness and naivety.
It'd be quite something if the Sports Direct business itself ends up in trouble financially though.