Liverpool's Luis Suarez has been handed an eight-match ban and a £40,000 fine by the Football Association after being found guilty of racially abusing Manchester United's Patrice Evra.
The Uruguay striker, 24, clashed with the France defender during the 1-1 draw at Anfield on 15 October.
Suarez, who denied the allegations, has 14 days to appeal against the decision.
He tweeted: "Today is a very difficult and painful day for me and my family. Thanks for all the support."
Liverpool, who had backed their player throughout the case, said the club was "very surprised" by the decision, while manager Kenny Dalglish said on Twitter that he was "very disappointed".
The Reds boss added: "This is the time when Luis Suarez needs our full support. Let's not let him walk alone."
The six-day hearing, which concluded on Tuesday, was told Suarez used "insulting words", which included a reference to Evra's colour.
A Liverpool statement said: "We find it extraordinary that Luis can be found guilty on the word of Patrice Evra alone.
"No one else on the field of play - including Evra's own Manchester United team-mates and all the match officials - heard the alleged conversation between the two players in a crowded Kop goalmouth."
The club added: "It appears to us that the FA were determined to bring charges against Luis Suarez, even before interviewing him at the beginning of November.
"Nothing we have heard in the course of the hearing has changed our view that Luis Suarez is innocent of the charges brought against him and we will provide Luis with whatever support he now needs to clear his name."
But Liverpool have questioned whether the FA also intends to charge Evra with making abusive remarks to an opponent.
The Anfield statement added: "Evra admitted himself in his evidence to insulting Luis Suarez in Spanish in the most objectionable of terms.
"Luis, to his credit, actually told the FA he had not heard the insult."
TIM VICKERY COLUMNContinue reading the main story
Suarez's eight-game ban smacks of the FA seizing on a chance to score a political pointRead more of Tim's column
The FA said the penalty is suspended until after the outcome of any appeal which may be made by Suarez.
Its statement added: "The reason for this is to ensure that the penalty does not take effect before any appeal so that Mr Suarez has an effective right of appeal."
Piara Powar, executive director of Football Against Racism in Europe (Fare), believes the governing body's decision is a landmark judgement.
He told BBC Radio 5 live: "This is the first time we have seen an insight into what is said between players on the pitch, and what may have been commonplace between players in the past.
"This is a big moment and I would say that the FA have dealt with this in the right way. They have taken their time and taken independent advice.
"No one takes any pleasure from seeing him found guilty like this but it is an interesting judgement."
Powar said Fare has taken advice on the abusive word used by Suarez and the context of similar words in South American dialect.
He added: "If it is used in a friendly fashion then it is acceptable, it turns immediately to a hostile meaning if it used as an offensive word.
"Taking the context of that game, it is difficult to see how he would have used it in a friendly way."
Suarez, who is facing a separate charge from the FA over an alleged abusive hand gesture he made as he left the pitch following Liverpool's 1-0 defeat by Fulham on 5 December, told media in Uruguay that he "called him [Evra] something his team-mates at Manchester call him".
Evra made his claims immediately after the match and was quoted as telling French television station Canal Plus: "There are cameras, you can see [Suarez] say a certain word to me at least 10 times."
The Frenchman reported his complaint after the game to match referee Andre Marriner, who included it in his report.
Chairman of anti-racism group Kick It Out Herman Ouseley said: "The FA has shown leadership and intent through what has clearly been a difficult and complex complaint to deal with, and invested time and expertise to ensure this outcome.
"It has demonstrated that it will not stand for discrimination, something organisations such as Fifa and Uefa should take heed of."
But he added: "This charge is not saying Luis Suarez is a racist. It's saying, on this occasion, he used racist language.
"It doesn't make him a bad guy - he needs to learn what is acceptable."
Professional Footballers' Association chairman Clarke Carlisle thinks the decision is "100% correct".
He told BBC Radio 5 live: "There are definitely cultural differences for a lot of players coming from South America and from the continent into England.
"But even though those differences do exist, we still expect people who come and work here to adhere to the standards and the laws of this land.
"It's wholly acceptable in parts of the Middle East to chop off the hands of thieves but we wouldn't tolerate it here and it's just the same when it comes to racism."
PFA chief executive Gordon Taylor added: "I was surprised at the severity of the punishment - bearing in mind the length of time the case took. That suggested there was some doubt about the claims.
"But it shows the FA must have some compelling evidence."
Taylor also believes clubs tend to adopt a "them and us" stance against the FA when their players are investigated by Soho Square bosses.
He said: "They almost automatically support their players. But some things are bigger than clubs, players and even the game itself. Racism is one of them."
LUIS SUAREZ FACTFILE
Born 24 January 1987 in Salto, Uruguay
Makes professional debut with Nacional in 2005
Makes debut for Uruguay against Colombia in February 2007 and is sent off in the 85th minute
Joins Ajax in August 2007 in a deal reportedly worth £6.3m
In 2010, he scores 33 goals in 35 matches for Ajax before helping Uruguay reach the semi-finals of the World Cup. He is sent off in the quarter-final
In November 2007, he is banned for seven matches after being found guilty of biting PSV's
Signs for Liverpool in January 2011 in a deal worth up to £22.8m
Patrice Evra makes an allegation of racism against the striker in October and, after being found guilty, he is banned for eight matches and fined £40,000
SELECTED FOOTBALL BANS
1964: David Layne, Peter Swan and Tony Kay (life bans for betting on their team to lose, later reduced to 7 years)
1988: Paul Davis (9 matches for punching opponent)
1995: Eric Cantona (9 months for attacking supporter)
1998: Paolo di Canio (11 matches for pushing referee)
2003: Mark Bosnich (9 months for failed drugs test)
2003: Rio Ferdinand (8 months for failing to take drugs test)
2005: David Prutton (10 matches for pushing referee)