Hello @brod_104
I have looked into your save file.
Basically what has happened is you listed Marco Hiller as the 'Cup Keeper' which would mean Hiller would be expecting to play the DFB-Pokal & Champions League games but you only played him in the DFB-Pokal and two champions league games (Cup GK means ''all cup games''), that is why the player is upset.
If you only intended to play Hiller in the DFB-Pokal you should have selected 'Domestic Cup Keeper' instead.
I hope this was helpful.