Gayle was shown a controversial red card for two bookable offences by referee Graham Scott in Albion's 2-1 defeat to Villa, and that carries an automatic one-game ban.
But his suspension has been extended to two games by the FA because an earlier ban for deceiving an official adds another game on to this suspension.
It means Gayle's season is over, regardless of whether the Baggies overturn the one-goal deficit at The Hawthorns on Tuesday night.
Albion cannot appeal the red card because it was for two bookable offences and not a straight red.
Gayle was shown a yellow card for time-wasting before another one two minutes from the end for a challenge on Jed Steer.
Caretaker boss Jimmy Shan disagreed with both bookings.
"To my mind, every time the ball went out he had an intent of walking towards to the ball," said Shan.
"It's a new one on me if you have to jog and sprint to restart every time the ball goes out.
"No problem with me with the referee discussing that with him and trying to hurry him up, but not once did Dwight stand still, every time he's walking to take the throw-in.
"The second one, for myself, he's got every right to contest the ball."
Gayle received a two-game ban earlier this season for deceiving an official to win a penalty.
Some Albion supporters are claiming video replays from today's game suggests there may have been little or no contact when Jack Grealish won a penalty under a sliding challenge from Kieran Gibbs.
The FA are planning to read the referee's report before deciding whether to take any further action.