Tony -

On your main clubhouse page it'll say "Roster for Fri, Oct. 31" over your current roster. If there's no opponent listed under "NEXT" then that person isn't playing. Just make sure everyone has an opponent.

Hey - Why am I telling you this? Now it'll be tougher to pass you!

P.S.
"Every roster slot must be filled to have a valid team." -- that's not entirely accurate. You don't need a full roster to accumulate points. This allows you to keep a player who isn't playing to save his original salary for when salaries rise (or fall) Sunday night/Monday morning...