London - With Manchester United manager Jose Mourinho and Manchester City boss Pep Guardiola set for the 17th instalment of their bitter rivalry in Saturday's derby at Old Trafford, we looks back at five classic encounters between the old rivals:
Inter Milan 3 Barcelona 1, Champions League semi-final first leg, April 2010
Responding in bullish fashion after Inter were brushed aside by Guardiola's Barcelona in the Champions League group stages, Mourinho insisted he would relish a semi-final rematch.
Mourinho got his wish in an acrimonious clash that lit the fuse on the pair's rivalry.
Pedro gave Barca the lead, but Inter roared back with goals from Wesley Sneijder, Maicon and Diego Milito.
Even in the afterglow of such a famous result, Mourinho couldn't resist taunting Guardiola over several rejected Barca penalty appeals, referencing Chelsea's controversial Champions League semi-final against the Spaniards: "A year ago Chelsea were crying and Barca were laughing with the referee".
And Mourinho's provocation of Guardiola was only just beginning as he embarked on a jubilant sprint across the Nou Camp pitch after a 1-0 second leg loss narrowly secured 10-man Inter's place in the final. "It is the most beautiful defeat of my life," he gloated.
Barcelona 5 Real Madrid 0, La Liga, November 2010
Joining Real put Mourinho in direct confrontation with Guardiola and the simmering feud boiled over after Barca inflicted one of the most chastening defeats of his career.
Mourinho's first El Clasico quickly turned sour as Xavi and Pedro put Real in control.
Real were reduced to targeting Messi with a series of increasingly cynical fouls that became the hallmark of Mourinho's meetings with Guardiola's men, but the Barca forward wasn't intimidated and set up David Villa for the third and fourth goals.
Jeffran sealed Mourinho's humiliation before Real's Sergio Ramos was sent off, leaving Guardiola to take a jab at Mourinho's tactics as he said: "I'm proud the whole world has seen how we play football."
Barcelona 0 Real Madrid 1, Copa del Rey final, April 2011
Meeting for the first time with silverware at stake, Mourinho secured the maiden trophy of his Real reign at Guardiola's expense and ended the club's 18-year wait to win the Spanish Cup.
A brutal encounter was decided in the first period of extra-time when Real forward Cristiano Ronaldo converted Angel di Maria's cross.
Di Maria was sent off in the closing moments, but Real held on for what Mourinho labelled "a fantastic triumph," while Guardiola grumbled the linesman "must have great eyesight" after a Pedro strike was ruled out for offside.
Real Madrid 0 Barcelona 2, Champions League semi-final first leg, April 2011
With the animosity between the managers at fever pitch, their spiteful clash for a place in the final of Europe's elite club competition poured more fuel on the fire.
The sparring started in the build-up when Mourinho ridiculed Guardiola's comments about that offside goal in the Spanish Cup -- "A man who criticises good decisions. This is completely new to me," he said.
Guardiola was incensed, ranting: "He's been winning off the pitch all season. In the press room he is 'el p*** jefe' (the f*****g boss) and the one who knows more than everyone else".
But it was Guardiola was had the last laugh. Barca's fired up players gave their boss a standing ovation when he returned to the hotel and made Mourinho pay by effectively booking their place in the final with two late goals from Messi after Real defender Pepe was sent off.
Mourinho, banished to the stands for protesting, had a typically sour verdict. "One day, I would like Josep Guardiola to win this competition properly," he moaned.
Barcelona 3 Real Madrid 2, Spanish Super Cup second leg, August 2011
The cold war between Mourinho and Guardiola showed no signs of thawing and their relationship hit a new low following yet another ugly encounter.
With the scores level at 2-2 from the first leg, Andres Iniesta bagged Barca's opener only for Ronaldo to equalise five minutes later.
Messi restored Barca's lead, then Karim Benzema equalised eight minutes from time, sparking a frantic finale in which Messi volleyed the winner before Real's Marcelo was sent off for a reckless tackle on Cesc Fabregas.
The ensuing brawl saw Real's Mesut Ozil and Barca's David Villa shown red cards, while Mourinho poked Barca assistant Tito Vilanova in the eye.
Barca defender Gerard Pique had seen enough. "Someone has to take action. Mourinho is destroying Spanish football," he fumed.