It would be great if somewhere on the homepage (eg. your Notifications system or even clearer ideally) I can see a big prompt/warning that a contest is starting soon and I have a player selected who is confirmed not playing (eg. after the final teams are announced for AFL and NRL 90 and 60mins out).
Probably not business viable for you, but an ever better outcome would be for your system to automatically cancel an entry at the contest cutoff if it contained a confirmed non-playing player (and I could switch this auto-cancelling off and on in my settings in case for whatever reason a user didn't want you to auto-cancel)