"The actions that we glorify become odious when performed by the enemy." Penned by the famous French writer Anatole France, those words sum up the feelings experienced by football fans whenever their idols switch sides and run out for their eternal rivals. The history of the game is littered with such cases, and from Johan Cruyff through Mo Johnston to Sol Campbell, FIFA.com recalls some of the most dramatic and painful changes in allegiance.
In 1990 the city of Florence was shaken by two days of rioting that left 50 people injured. The cause of the disturbances was the departure of Viola idol Roberto Baggio to Juventus. Still irked at their recent UEFA Cup final defeat to the Turin giants, the Fiorentina tifosi viewed his decision to move north as an act of betrayal, despite his protestations that he had been forced to accept the transfer.
In a subsequent league meeting between the two sides in April 1991, the attacking midfielder showed his depth of feeling for his former club by refusing to take a late penalty and saluting the Fiorentina fans in a surreal end to the game. As he walked from the pitch to the sound of catcalls and applause, Baggio even picked up a Viola scarf that had been thrown from the stands and put it round his neck.
Another player at the centre of a similar storm was Luis Figo. After five seasons with Barcelona, the Portuguese midfielder followed the path taken by his predecessors Bernd Schuster and Michael Laudrup and signed for Real Madrid in 2000 for a then-record fee of €67m.
Stunned by Figo's defection to their hated rivals, the Barça faithful made their feelings known when he returned to the Camp Nou with his new team-mates for the clásico three months later. The 98,000 crowd voiced their displeasure at their one-time hero for 90 long minutes, prompting Figo to comment after the game: "I'm more determined than ever now to triumph with Real Madrid." In a later derby meeting in 2002, irate fans even threw a pig's head at the Portuguese international. The object has since gone on display in a museum in the Catalan capital.
After returning to the Netherlands following a successful stay at Barça, Dutch legend Johan Cruyff incurred the wrath of Ajax fans in 1983. Piqued by the Amsterdam club's refusal to extend his contract, Cruyff promptly joined arch enemies Feyenoord, warning his former team-mates before he left that he would win the league with his new team. True to his word, Cruyff went and did just that.
We've got Jesus, you've got Judas
Perhaps the most notorious transfer controversy in Scottish football involved international striker Mo Johnston. After spending two seasons with French club Nantes in the late 1980s, the former Celtic striker and self-proclaimed Bhoys fan was anxious to return home. A hero in his three seasons at Celtic Park between 1984 and 1987, Johnston appeared set for a return to his former club, even posing in the green-and-white shirt, only for Rangers manager Graeme Souness to step in and lure him to Ibrox.
In the process Johnston became the first Catholic player to sign for the Ibrox club, triggering furious reactions in both the green and blue halves of the city, with Celtic fans dubbing him 'Judas' and some Rangers supporters burning their season tickets in disgust. "People in the west of Scotland get too caught up in it all," Johnston would later recall. "I realised what I was doing and it's something I'll always have to live with but that doesn't bother me. No, the fact that I had grown up supporting Celtic was never a problem for me - the problem was the attitude of some of the Rangers supporters."
Fierce passions are aroused in France whenever Paris St Germain and Marseille enter into transfer negotiations together, giving fans on both sides a chance to vent their fury at the 'traitors' jumping ship. One of their targets in recent years was Frederic Dehu, who left the Parisians for the Velodrome in 2004. On his return to the Parc des Princes for a match in November 2004, the defender was met with a banner that read: 'We have Jesus (in reference to the bearded, long-haired Colombian defender Mario Yepes), and you have Judas.'
From Jean Djorkaeff in 1970 to Claude Makelele in 2008, the list of players who have sported the jerseys of France's two fiercest rivals has grown over the years, and includes the likes of Fabrice Fiorese, Florian Maurice, George Weah, Lorik Cana and Jerome Leroy.
Such is the animosity between Tottenham Hotspur and Arsenal that few players have dared to cross the North London divide. Having made more than 250 appearances for Spurs, Sol Campbell's status as a White Hart Lane legend seemed assured for life. However, when he was courted by some high-profile members of the European elite in 2001, the imposing centre-half decided to join the Gunners of all teams, a decision for which Spurs fans have never forgiven him.
Gatti, the king of Buenos Aires
During his celebrated career, goalkeeper Hugo Orlando Gatti enjoyed success with the two biggest clubs in Argentina. In 1964 River Plate spared no expense in putting together a lucrative four-year contract for El Loco (The Madman). Gatti stayed with Los Millonarios for a further eight years before then joining Boca Juniors, where he would call time on his career in 1989. In a 13-year stint with the Xeneizes, he wore the blue and yellow jersey on 372 occasions, and appeared in no fewer than 38 superclásicos in all, a record that still stands today.
Our tour of the world ends in Brazil with the story of the hugely talented Romario. Between 1985 and 2008, the 1994 FIFA World Cup™ winner signed on four separate occasions for Vasco de Gama, where he started and finished his career, and three times for Rio foes Flamengo. There are few teams in world football that despise each other with such passion, and Romario's last contribution to the heated rivalry was to score the 999th goal of his career for Vasco in a derby clash with the Rubro-Negro. No doubt the man they call O Baixinho (Shorty) would have loved to have added another goal to his tally that day.
Ronaldo, his team-mate and then successor at the spearhead of the Brazil attack, is another player who knows all about big footballing rivalries, having represented both Barcelona and Real Madrid with distinction and Milan adversaries Inter and AC.
Have your say
Eric Cantona's switch from Leeds United to Manchester United, Aime Jacquet's from St-Etienne to Lyon, Ronald Koeman's from Ajax to PSV Eindhoven and Andreas Moeller's from Borussia Dortmund to Schalke 04. These are just some of the big-news transfers that have taken place over the years involving two rival clubs. Can you think of any more? Click on 'Add your comment' below and let us know.