West Ham star Vladimir Coufal could miss the game against Arsenal next week if he picks up a booking against Manchester United on Saturday.
The Hammers were hammered 5-1 by Liverpool in the League Cup quarter-final on Wednesday night and Moyes desperately needs a result against Manchester United to bounce back from what was a poor performance from them.
Coufal has played every game this season, missing only three Europa League fixtures and one Carabao Cup match.
The defender has 5 assists in 17 league games and is considered to be a vital player for Moyes.
But he will need to be very careful against Manchester United. He is on four yellow cards and the new Premier League rule states that 5 bookings in the first 19 games leads to a one-game suspension.
If he picks up a yellow against United, he will miss the game against Arsenal on the 28th December.
A win tomorrow will take them above Manchester United in the table.