Training ground bust-ups are an interesting part of modern football. Above all, they remind us how there is a very fine line between mega-rich athletes with the greatest riches, cars and homes, and petulant five-year-old children.
Aside from that, though, such rivalries and struggles on the training pitch serve as great indicators of players' temperaments and the chemistry within a team.
Over the years, we've seen countless reasons why players have opted for the exit door, and why their clubs have seen fit to put them on the transfer list. More often than we may think, it boils down to their attitudes.
Also read: 7 teammates who hated each other
Here then, is a list of five players who were sent packing after bust-ups with their teammates.
5. Oguchi Onyewu – vs. Zlatan Ibrahimovic at AC Milan
It is a clash of the titans – a 6' 4" American centre-back, renowned for his unprecedented strength and physique and, well, Zlatan Ibrahimovic. The two were in the same squad at AC Milan, although Onyewu didn't play a single league game during his three-year spell with the Italian giants.
Ibrahimovic is a well-recognised antagonist, so it's no surprise that it was the energetic, teasing Swede who started the feud.
In a training session one day it is believed that Zlatan put in a reckless challenge on Onyewu, to which he angrily responded. The club's training session was cut short that day as it is thought the two began throwing serious punches at one another, with teammates needing to separate the duo. In essence, it has been suggested that the altercation resulted in Zlatan sustaining a broken rib.
Onyewu would go on loan to FC Twente two months later and would not return to Milan to play another game, although neither player received any serious punishment.
4. Graeme Hogg – vs. Craig Levein at Hearts
It's not only cup semi-finals and training grounds that are affected by heated teammate bust-ups, but friendly, yes FRIENDLY, matches too. It was August 1994 and Hearts were facing Raith Rovers in a pre-season friendly.
Just before half time, Rovers went 1-0 up and nearly scored another, prompting Hearts' centre-backs Graeme Hogg and Craig Levein to lock horns, arguing over who should've been marking the individual who nearly scored the second goal.
The two began to fight, and Levein threw a punch which broke Hogg's nose. Both players were sent off and Hogg received his red card as he was stretchered off the field. Levein was stripped of his captaincy and got a twelve game ban, whilst Hogg got a ten-game ban.
Levein though remained at Hearts for the rest of his career, while Hogg was sent to Notts County the following season.
3. John Hartson – vs. Eyal Berkovic at West Ham
Former Celtic, Arsenal and West Ham forward John Hartson holds the title of the first-ever footballer to be charged for an incident on the training ground after his collision with Eyal Berkovic was caught on camera.
Hartson had put in a meaty challenge on the Israeli midfielder, leaving him twisting and turning on the floor. He then attempted to help his teammate up, only for Berkovic to lash out and punch Hartson in the leg.
This only antagonised the striker, who proceeded to kick him in the head, rendering Berkovic paralysed and unable to eat for two days. At the time, the Israeli claimed, "If my head had been a ball, it would have been in the top corner of the net."
The punishment for Hartson was a three-game suspension and a fine of £20,000. He fell out of favour and suffered a loss of form as a result and was sold in the following January transfer window to Wimbledon.
2. Joey Barton – vs. Ousmane Dabo at Manchester City
Joey Barton and conflict seems as natural a combination as strawberries and cream, so it's no real surprise to see him on this list. Although Barton later claimed that it was a "relationship breakdown" with Manchester City's then-manager Stuart Pearce which led to him leaving the club, it's difficult to dispute the argument that, had he not involved himself in a fight with Ousmane Dabo, he would have remained at the club for a lot longer.
Following a few crosswords in training, Dabo and Barton got caught up in a fight in which the Englishman inflicted several punches on the Frenchman, hospitalising him and leaving him with a detached retina, amongst other knocks to the head.
Greater Manchester Police were alerted regarding the incident and Barton pleaded guilty. The midfielder was then issued a £3000 fine as well as a four-month suspended prison sentence.
1. Dani Osvaldo – vs. Jose Fonte at Southampton
Dani Osvaldo did very little to appease the growing discontent aimed at him by supporters when he tussled with fan-favourite Jose Fonte during a cold January training session. The Argentine, who plays for Italy on the international stage, became the club's record signing for just over £15 million in 2013 but just a year later he hit rock-bottom for the Saints.
Rumours suggest that both Fonte and Osvaldo were antagonising each other and were frequently winding one another up in a training match, when Fonte put in a rather aggressive challenge on the forward to win the ball.
Osvaldo was left fuming and leapt up, locking face-to-face with Fonte. Before other players were able to separate the pair, Osvaldo head-butted Fonte, drawing blood and leaving the defender with a black eye and a broken nose.
Pochettino and the Southampton contingent were left mortified and the club suspended the Italian for two weeks, after which he was loaned out to Juventus for the rest of the season. Osvaldo didn't leave immediately but would not feature for Southampton the following season either, spending it loaned out at Inter Milan and Boca Juniors before the Saints finally ripped up his contract in the summer of 2015.