He has to take some responsibility for his fitness. Is it a lack of professionalism on his part, or a lack of guidance and control from the club?
I do not know how the club manage players but is it not reasonable to set parameters for fitness for each player with boundaries and targets. A range for say weight, cardio, speed, agility and stamina etc. tailored to suit the attributes required for each player and position.
A player should be tested regularly and if outside an agreed range, they should be required to do extra work, be given a strict diet plan to follow all under supervision. There will be some players that find this easy, say Basham and will have no issues, others like Moose will need to work harder and adjust their lifestyle to succeed, that's life.
I am sure a fully fit and resilient Moose would be a big player for us, and score a hat full of goals at this level (given the service).
If only he could stay fit.
HH