The pair constantly went toe-to-toe during the intense rivalry between the Gunners and the Red Devils and had a famous bust-up in the tunnel at Highbury in 2005 - with Sportsmail columnist Graham Poll the referee caught in the middle before the game had even started.
All smiles: Patrick Vieira and Roy Keane strike a cordial image
Keane won seven Premier League titles to Vieira's four and the pair were on four FA Cup wins each until Vieira added a fifth medal to his collection after Manchester City's win in May.
Keane was captain of the 1999 Treble-winning side but missed the Champions League final through suspension while Vieira wins hands down on the international front.
Best of enemies: Keane (left) and Patrick Vieira come to blows in 2005
The Frenchman was part of the successful Les Bleus team at the 1998 World Cup and Euro 2000.
Keane once criticised Vieira for representing France rather than Senegal where he was born while the Gunners legend hit back by having a dig at his rival for walking out on the Ireland team at the 2002 World Cup.
The pair, now older and wiser, were in Spain on Wednesday as Manchester City - where Vieira is football development executive - beat Villarreal 3-0 to keep their Champions League bid on track.
Watch the video of Keane and Vieira's tunnel trouble
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Source: Daily Mail
Source: Daily Mail