Swansea City have lost their appeal against goalkeeper Lukasz Fabianski's sending off in the 3-1 Premier League defeat by West Ham.
Fabianski was shown a 68th-minute red card by referee Chris Foy for a professional foul on Diafra Sakho.
The Welsh club appealed to the Football Association, but the governing body upheld the decision on Tuesday.
The Poland international will now miss Sunday's Premier League match against Tottenham at the Liberty Stadium.
A statement from the FA read: "Swansea City's Lukasz Fabianski will serve a one-match suspension with immediate effect after his claim of wrongful dismissal was dismissed following an Independent Regulatory Commission hearing today.
"Fabianski was dismissed for denying a goal scoring opportunity.''
Television replays had suggested the Senegal international handled the ball before being fouled by Fabianski.
"It should have been handball and a free-kick to us," said Swansea manager Garry Monk after the game.
"It was poor defending in the lead up to the situation from Ashley Williams and Fab comes out, but before there's any contact or anything like that the player handled it past our keeper."
The red card came during a three-minute period when West Ham took the lead and the Swans were reduced to 10 men.
Wilfried Bony's seventh Premier League goal of the season had put Monk's team ahead in the 19th minute, but two headed goals from Andy Carroll put the Hammers in control before the red card and Sakho's emphatic 87th-minute strike.
Monk had no complaints about the result, but was unhappy with his team's performance in a match which saw the Swans stay in eighth spot.
"We didn't reach the levels we have been reaching this season and that's the first time I can say that in all the games that we've had so it's disappointing," said Monk.
"I think we only really got playing anywhere near that kind of level when we actually went down to 10 men, but it shouldn't have to take that sort of incident for us to kick into life.
"Unfortunately there was some poor defending and we kind of gifted them the win.
"We talked about being brave with the ball and moving it quickly, one or two touch and you saw with our goal if we did that we could cut them open.
"We didn't do it enough and we picked the wrong decisions with the ball and really caused our own problems.
"Unfortunately, but probably deservedly, we lost the game."