West Ham will appeal the red card picked up by Sofiane Feghouli in the 2-0 defeat to Manchester United on Monday.
Feghouli was shown a straight red card by referee Mike Dean in the 15th minute with the game goalless following a sliding challenge with United defender Phil Jones.
United were able to make their extra man count in the second half, with Juan Mata and Zlatan Ibrahimovic grabbing the goals to earn Jose Mourinho's side a sixth straight Premier League win.
Feghouli will serve an automatic three-match ban if the Football Association decide to uphold Dean's decision and miss the FA Cup tie with Manchester City, as well as the Premier League games against Crystal Palace and Middlesbrough.
Following the match at London Stadium, West Ham manager Slaven Bilic told Sky Sports: "It was never a red card to be fair. It was a challenge from both of them.
"It was the other way round in terms of who did the more dangerous tackle. It was Jones. OK, he's carrying the ball but he went in with the scissors.
"Phil made a meal of it, but you can't blame him for doing that. Maybe he made a meal of it because he went with the dangerous one to save himself.
"You have to see who is doing our challenge. It's Feghouli, who very rarely makes a foul in the game. His foot wasn't high in the air and it wasn't deliberate.
"For me, that was the crucial decision in the game. That early - it killed us. It put the game in a totally different perspective."