There are some intense, tribal rivalries throughout the football world but there have always been players willing to cross the divide and risk alienating one or possibly two sets of supporters.
Some of those moves have worked out better than others and the negative experiences may influence the mindset of the modern day player.
However, there are sure to be individuals either brave enough or foolhardy enough to stir up a hornets' nest.
Player power famously increased after Jean-Marc Bosman won his case against the Belgian FA and UEFA in 1995, allowing individuals to leave clubs on a free transfer upon the expiration of their contracts.
Campbell, who had made his Tottenham debut in 1992, was aware of the significance of the verdict and his future was up in the air in the summer of 2001 as his contract approached its conclusion.
Tottenham were desperate to retain their captain and offered to make him the highest paid player at that point in their history. Campbell even gave them public assurances that he would sign on the dotted line.
However, that moment never arrived and Spurs fans were left stunned when it was announced that the England man would be joining bitter rivals Arsenal.
Campbell spent the next five seasons with the Gunners and was part of a hugely successful team which won two Premier League titles (2001-02 and 2003-04) and three FA Cups (2001-02, 2002-03 and 2004-05).
From a career point of view, he made the right decision because Tottenham, at that time, were not challenging for silverware.
Campbell won an FA Cup winners medal with Portsmouth in 2007-08, and returned to Arsenal for a brief, but far less controversial spell, which covered the second half of the 2009-10 season.
Luis Figo starred for four great clubs – Sporting, Barcelona, Real Madrid and Inter – but his status among Barca fans will be forever tainted by his decision to swap the Camp Nou for the Bernabeu in July 2000.
Figo joined Barcelona from Sporting in the summer of 1995 and soon became a fan favourite as he helped the club secure seven trophies, including two La Liga titles (1997-98 and 1998-99) and the 1996-97 European Cup Winners Cup.
However, his Barca contract included a release clause which was eventually triggered by Real Madrid, who completed one of the most controversial deals in La Liga history.
Figo was considered a pariah among Barcelona fans and was mercilessly booed upon his return for a La Liga fixture in October 2000 which the Catalans won 2-0.
The winger appeared shocked by the reaction and put his fingers to his ears. He also steered clear of the touchline whenever possible and passed up his role as Real's regular corner taker.
While Figo's first return to the Catalan capital was an experience best forgotten, he soon established himself as a key player for Real, where he won two league titles (2000-01 and 2002-03) and a Champions League (2001-02).
He finished off with a trophy-laden four-season spell at Inter where he was a four-times Scudetto winner.
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Eric Cantona is revered by Manchester United fans, who regularly sing his name, but he previously spent a roller-coaster 11-month spell with Leeds, who he helped to win the Division One title in 1991-92.
The Frenchman's relationship with Leeds manager Howard Wilkinson soon soured and he requested a transfer, asking to be allowed to join Manchester United, Liverpool or Arsenal.
United took the plunge and it quickly became clear that they had landed an absolute bargain.
Cantona starred in the United team which dominated the early years of the Premier League – landing four titles between 1992 and 1997 – and was part of two FA Cup final winning teams, scoring twice in a 4-0 success over Chelsea (1994) and the deciding goal in a 1-0 triumph over Liverpool (1996).
Manchester United completed another controversial deal in July 2009 by snapping up Michael Owen on a free transfer from Newcastle.
Owen had often been linked with a return to Liverpool, where he excelled in the early part of his career, but United offered him a two-year pay-as-you-play deal which took into account an injury-hit four-year-spell at Newcastle.
Owen's move to Manchester didn't go down too well with Liverpool fans but it worked out well enough for the player, who spent three years at Old Trafford and won a Premier League title in 2010-11.
He also famously scored the late winner in a dramatic 4-3 win over Manchester City to forever endear him with the United faithful.
Many Scottish football fans would argue that there was no more controversial transfer than Mo Johnston's move from Nantes to Rangers in 1989.
Johnston was established as a Celtic hero after a hugely successful spell between 1984 and 1987 when he scored 52 goals in 99 league games and won a league title in 1985-86.
He was largely expected to rejoin the Bhoys after a two-season spell with Nantes, but changed his mind and sealed a stunning move to Rangers, whose supports weren't universally keen on the deal.
The forward eventually won over large sections of the Gers' support and was part of the team which won Scottish league titles in 1989-90 and 1990-91.
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