Pep Guardiola and Jose Mourinho have become two of the games best managers. Between them, they've coached almost all of the biggest clubs in Europe, with Mourinho having spells at Real Madrid, Chelsea, Inter and Porto, while Guardiola has had stints at Barcelona and Bayern Munich.
The two now manage in Manchester, with Mourinho at United, and Guardiola across town at City. It's fair to say that the two men have had their differences since working together at Barcelona between 1996-2000, when Mourinho was a coach and Guardiola was a player.
Their relationship has become one of the biggest rivalries in football, and the two have been in opposite dugouts 16 times in their careers. We've picked five of those games that had fireworks not just on the pitch, but off it too.
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Barcelona 1-0 Inter Milan - April 2010
Although Guardiola's side won on the night, it was Mourinho who was celebrating at the final whistle. His side progressed into the Champions League final on aggregate, after winning the first leg 3-1. It was a tactical masterclass from Mourinho's Inter, who defended solidly with 10 men for over an hour. Only Gerard Pique's 84th minute goal could offer consolation for Barcelona, who were dumped out of the tournament.
At the final whistle, Mourinho ran down the touchline at the Nou Camp with his hands in the air, before saluting the Barca fans. They'd mocked him throughout the tie with cries of "the translator" relating to his time with the club in the 1990s. It was the Portuguese who had the last laugh though, as his side went on to win the whole tournament.
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Real Madrid 0-2 Barcelona - April 2011
With a place in the Champions League final on offer, tempers were always likely to flare in the semi-final second leg tie between Madrid and Barcelona,. Real were reduced to 10 men as Pepe was sent off just after half-time. In response to the decision, Mourinho was seen mouthing the words "well done" to the fourth official and was sent to the stands.
With Madrid down to 10 men and without a manager, Guardiola's side took full advantage and went on to win 2-0, booking their place in the Champions League final.
Barcelona 3-2 Real Madrid - August 2011
It was in another El Clasico that Guardiola's Barcelona shaded the Spanish Super Cup against Mourinho's Madrid, but events off the pitch overshadowed those on it. Marcelo’s late sending off sparked an injury-time brawl involving players and coaching staff. Mourinho was infamously accused of poking then Barcelona assistant coach Tito Vilanova in the eye, which he says to regret to this day. After the brawl was broken up, Barcelona went on to lift the Super Cup, giving Guardiola his 11th major piece of silverware in Spain.
Barcelona 1-2 Real Madrid - April 2012
With the La Liga title race going down to the wire, the winner of this clash would almost certainly go on to win the league. Cristiano Ronaldo scored the winner as Real Madrid beat their hosts at the Nou Camp and closed in on their first title in four years.
Mourinho was able to get one over on Guardiola that day, and he may have former club Chelsea to thank. The Blues beat Barcelona in a Champions League semi-final a few days before, and the Catalan club returned home tired and dejected. Real took full advantage.
Bayern Munich 2-2 Chelsea - August 2013
It was Guardiola who came out on top after the most recent meeting between the two coaches. But only just. The Super Cup put Mourinho's Chelsea side against Guardiola's Bayern Munich team, as the coaches took charge of one of their first competitive games since leaving their Spanish clubs.
Bayern lifted the trophy after winning on penalties, as Guardiola beat Mourinho in their last meeting for the foreseeable future.
With their last clash just under three years ago, the rivalry may have gone a bit cold. But as the two managers prepare to take charge of their Manchester clubs for the upcoming season, expect it to be hotter than ever when they meet at Old Trafford for the first Manchester Derby of the season on September 10th.
Who do you think will come out on top this season: Mourinho or Guardiola? Have YOUR say in the comment box below!