Hi Graham,

I can understand you are in a difficult situation, however, you need to get the balance right between doing the best for your team and also supporting your players. Personally, I would advise getting all your player together and explaining how changes may occur. Explain how you will be picking a squad upon how players train, work together and their overall performance. This should make your existing players work harder to try to make the team. 

It important to remember, if you are moving a player down, explain why and what they need to do to improve. This will place the player in control, as they should try to work on these to regain their place. 

Also, explain how changes may occur during the season and the squad is not fixed. This will give those players who didn't make the team the hope of moving up, and those already in the team will continue to work hard to retain their space. 

Hope this helps.