Swansea have lost their appeal to overturn Neil Taylor's red card at Nottingham Forest in the Championship play-off semi-final, first leg.
The defender was sent off after two minutes for a lunge on Lewis McGugan, but Swansea held on for a 0-0 draw.
A Football Association of Wales hearing on Monday morning dismissed the appeal ahead of the home second leg.
And Taylor will serve the first of his three-match ban against Forest on Monday night.
If Swansea beat Nottingham Forest he would also miss the play-off final at Wembley on 30 May.
Swansea had believed they had a good case to win an appeal.
"The club feels it has grounds for an appeal to the Football Association of Wales," read a Swansea statement following the first leg.
"After reviewing the video evidence... Swansea City can confirm that the club will be appealing against the red card issued to Neil Taylor in the first leg of the play-offs at Nottingham Forest on Thursday night."
Just 90 seconds had elapsed at the City Ground when Taylor caught McGugan on the thigh with his studs, as both players challenged for a bouncing ball with raised feet.
McGugan got to the ball first but was sent tumbling by the Wales defender and, with the Forest midfielder writhing on the floor, referee Mike Dean decided the challenge merited serious punishment.
In a post-match interview with BBC Wales Swansea City manager Brendan Rodgers admitted he understood why the referee thought the tackle warranted a red card.
"I can see why Mike has given it," Rodgers said. "I thought the officials were very good, I thought they were excellent tonight.
"That is something that Neil will have to learn from, the ball has bounced and contact wasn't quite as bad as it looked when you see the replays.
"But his foot was up, he sort of caught him in the abductor and in the emotion of the game he goes off."
Swansea's other concern was the injury that forced star striker Fabio Borini off at the City Ground, but Swansea have confirmed that the Italian will be included in the squad to face Forest at the Liberty Stadium.
The on-loan Chelsea forward went down off the ball after 56 minutes clutching the back of his leg and the fear was that the suspected hamstring problem would rule him out of the second leg.
But after being assessed by the Swansea medical staff on Saturday, the injury was diagnosed as bruising and Borini has a good chance of playing some part on Monday.
There is also good news for fellow striker Craig Beattie, who is fit again after a stomach bug ruled him out of the first leg against Forest.
Full commentary of Swansea City v Nottingham Forest is on BBC Radio Wales and on BBC Radio Five Live (1930-2200 BST). Highlights are on Match of the Day Wales on BBC One Wales (2340-0010 BST, repeated on demand on iPlayer)