They are the two managers who can claim to have transformed English football during the Premier League era. Arsene Wenger and Jose Mourinho brought a fresh approach and were hailed as revolutionaries. They were arch-enemies at the cutting edge of the game, but that was more than a decade ago.
Now, Pep Guardiola is changing perceptions. Wenger is heading towards an unseemly parting of the ways with Arsenal. Even though Mourinho's Manchester United side is currently second in the Premier League, he's generally perceived to be a manager in decline. Both won silverware last season. The FA Cup adorns the trophy room at the Emirates, and Mourinho brought the Europa League and the League Cup to Old Trafford. Yet both men have seen their reputations questioned.
Wenger had the biggest impact on the English game. He will leave the Emirates this summer with his legacy spoiled, but he helped shape the direction of the Premier League in the years before and after the millennium. He arrived in north London in 1996 and transformed Arsenal's attitude to fitness and nutrition. "He was less a coach than a physiologist," said Tony Adams, the captain of his first great team. "We did everything faster than we'd done before."
Back then, the Gunners played at a pace that their rivals struggled to match. The Premier League was already a very physical league, but Wenger turned things up a notch. There was a crucial difference: Wenger's teams added a high level of skill to power and quickness. He inherited an organized, disciplined and robust defence, with the peak of Wenger's Arsenal career coming in 2003-04 when his "Invincibles" team went through the league season unbeaten.
Mourinho arrived at Chelsea in the immediate aftermath of that dominant campaign. He matched, and even surpassed, Arsenal's physicality. Chelsea were less flamboyant than the Gunners, but Mourinho was a coach. He targeted Wenger as his main rival and the relationship between the two men turned ugly because the Chelsea manager practised psychological warfare against his adversary.
Mourinho likes to think of himself as one of the catalysts for Wenger's long, slow decline, the beginning of which coincided with Mourinho's arrival in England. Yet the causes were deeper: in short, coaching and organization are not Wenger's strong point.
When Chelsea (or other sides without the skill) matched Arsenal's pace and power, Wenger tried to change the style of his team. The old guard, who were responsible for his early success in England, were moving towards the end of their careers and were replaced by a different type of player. Wenger went from Patrick Vieira to Cesc Fabregas as the key man in midfield. During the Highbury years, Arsenal had strength and technical ability. Once they made the move to the Emirates, technique reigned.
Stewart Robson, the former Arsenal midfielder and long-term critic of the manager, believes a lack of organization is Wenger's biggest flaw. "They are not prepared," he said. "They try and play off the cuff. There's no plan. There's no coaching." This was brutally obvious during Arsenal two 3-0 defeats by Manchester City. The Gunners entered the Carabao Cup final and the Premier League game that followed with only a vague blueprint for taking on Guardiola's team. They were humbled twice.
Meanwhile, Mourinho's detractors complain about the opposite problem. The 55-year-old has been suspicious of flair players throughout his career and prefers disciplined, hard-working types. United are staid and dull despite the presence of Paul Pogba, who appears bogged down by the team's tactics.
Ultimately, Mourinho is still committed to producing big, powerful sides. Since his arrival at Old Trafford, the majority of incoming transfers have been tall players. Only Alexis Sanchez and Henrikh Mkhitarayan, who were swapped for each other in January, are shorter than six foot, and Mourinho quickly lost faith with the Armenia international. Sanchez's work-rate makes him much more a Mourinho player and currently, Mkhitarayan is struggling to make an impact at Arsenal.
The United manager is under less pressure than Wenger, but there have been grumbles from the crowd at Old Trafford and from former players. Paul Scholes was particularly critical of United's performances of late, identifying one of the problems with United during Mourinho's tenure. "They need to liven up and find some energy from somewhere," said the retired midfielder, and the team's lack of energy reflects the manager's mood.
Mourinho's demeanour has been generally downbeat since he moved to Manchester. He lacks the vitality and wit that he showed especially in his first spell at Stamford Bridge, back in the days when he was jousting with Wenger. For the past two years, he has looked like a man who is not enjoying football; as such, his team appear to be taking as little pleasure from the game.
Wenger is a man who is still infatuated with the sport. When Arsenal win, he radiates happiness and is full of bonhomie. When they lose, the 68-year-old radiates frustration and anger, frequently looking for scapegoats. Often, he focuses on the officials. In public, at least, he rarely calls his players to account. For too long, Wenger was omnipotent at the Emirates, but his supporters in the boardroom, in the dressing room and in the stands are now turning against him. His exasperation is palpable.
There are skeptics in the Old Trafford hierarchy, too, and a growing number of fans question whether Mourinho is betraying United's traditions of attacking football. The Portuguese is in a much more secure position that his old sparring partner. Mourinho will outlast Wenger. How much satisfaction that will bring the United manager is anyone's guess.
The impact of Guardiola (and, to a lesser extent, Jurgen Klopp at Liverpool) has thrown Wenger and Mourinho's weaknesses into sharper focus. Their methods look tired in comparison with the Premier League's new generation of managers.
Wenger, for one, knows his time is running out. "You go up the stairs and come down in a lift," he said, when talking about how long a manager's career takes to build and how quickly it can go wrong. He is not quite right there; bluntly speaking, he's simply been in the throes of a long decline.
Mourinho has started the same lengthy process. He can still arrest the slide but needs to recover some of his swagger quickly or he will go down the same road as his old antagonist before too long.