Footballers are expected to fight tooth and nail for every goal and every point, but some take that too literally. It's a rare sight to see a proper brawl on a football field, and an even rarer one to see two teammates coming to blows.
But sometimes the red mist descends, friends become foes, and we all cheer - because let's be honest, there's nothing better than two teammates going hell for leather over one misplaced pass.
Here are six times when club allegiances didn't get in the way of a good old-fashioned scrap.
Lee Bowyer vs Kieron Dyer
Lee Bowyer was a notoriously hot-headed character during his playing days, and never was that more in evidence than during this most famous of on-pitch bust-ups in 2005.
Newcastle were 3-0 down at home to Aston Villa and had already been reduced to ten men after Steven Taylor's handball. Frustrations boiled over when Dyer chose a backwards pass instead of going forwards in search of a goal, prompting a few choice words from Bowyer.
The two men came to blows moments later and had to be separated by players from both sides before any proper punches could be landed.
Dyer was given his marching orders first before Bowyer, his torn shirt providing evidence of his guilt, was also dismissed. Both men were fined and given six-match bans for losing their cool.
Jens Lehmann vs Marcio Amoroso
Jens Lehmann was certainly one of the most interesting characters in English football when he played for Arsenal between 2003 and 2008, but they should have expected nothing less after his antics in Germany.
Lehmann became the first Bundesliga keeper to be sent off four times in his career when he was shown a red card against Schalke in 2003 - for fighting with one of his Borussia Dortmund teammates.
After Dortmund conceded a goal, Lehmann felt that Marcio Amoroso was at fault and charged half the length of the pitch to confront him, physically shoving the Brazilian midfielder until referee Herbert Fandel intervened and showed him the now-familiar red card.
Graeme Le Saux vs David Batty
"Before the match I told my players they will be playing against 11 guys ready to fight for each other...not with each other."
Spartak Moscow manager Oleg Romantsev neatly summarised this fight between Blackburn duo Graeme Le Saux and David Batty, which epitomised Rovers' disastrous Champions League campaign in 1995/96.
Le Saux, who later revealed that he and Batty had been at each other's throats for weeks in training, miscued a pass and received an earful from his teammate. He rose to the provocation but only threw a couple of punches before Tim Sherwood separated the pair.
Amazingly, neither was sent off, but Rovers went on to lose 3-0 and were knocked out at the group stage.
Fernando Ricksen vs Vladislav Radimov
You wouldn't expect to see two teammates fighting each other in a competitive game, let alone a friendly match. But Fernando Ricksen always had a loose grasp of the word "friendly".
Just two weeks after joining Zenit St Petersburg on loan from Rangers in 2006, Ricksen returned to Ibrox and nearly came to blows with his former teammates after hacking down Chris Burke, who had already been off the pitch for treatment.
That was a near-miss, but Ricksen was at it again the following summer in a friendly against Malaga. An argument with Zenit captain Vladislav Radimov ended with punches thrown and both men were sent off.
Ricksen wanted to continue the fight once the two players had left the field and had to be kept away from Radimov by Zenit staff.
Ricardo Fuller vs Andy Griffin
Stoke gained a reputation for being a physical side under Tony Pulis, but it was usually the opposition who bore the brunt.
The visit to West Ham in December 2008 was a rare exception. The Potters were winning 1-0 when Andy Griffin failed to clear a simple ball into the box and Carlton Cole pounced to equalise.
As Stoke prepared for the restart, Ricardo Fuller and Griffin engaged in a frank exchange of views which culminated in Fuller slapping his captain across the face.
His teammates restrained him and after the situation had been defused, referee Mike Jones had no choice but to send the Jamaican for an early bath. Just to rub salt in the wounds, Stoke went on to lose 2-1.
Emmanuel Adebayor vs Nicklas Bendtner
Arsenal hadn't lost to Tottenham in nine years ahead of this League Cup semi-final second leg in 2008, but that was all about to end on a chastening night for the Gunners.
Arsenal were 4-1 down to their arch rivals and heading out of the competition in embarrassing fashion. Nicklas Bendtner had scored one of the goals, inadvertently heading the ball into his own net.
Adebayor, who scored Arsenal's consolation, riled Bendtner with a pointed comment, and the Dane responded by showing his teammate the middle finger. Then things turned violent as Adebayor laid a headbutt on Bendtner.
Despite Bendtner having a cut as evidence, Adebayor was not punished because replays proved inconclusive. Unsurprisingly, he was sold to Manchester City at the end of the season.
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