It's been almost a month since the explosive Manchester derby at Old Trafford that became almost as famous for the action after the game as the football that transpired during it.The actual game ended 2-1 to the blue half of Manchester and it allowed City to move some 14 points clear at the top of the Premier League.However, after the game, tensions ran high in the Old Trafford tunnel and both sides became involved in a fracas that has never been truly explained.While Mikel Arteta is said to have suffered a facial injury and Jose Mourinho is alleged to have squared up with City goalkeeper Ederson, only those two sets of players will truly ever know what happened.Still, the game itself was a feisty affair and you could tell the home side knew it was a make-or-break game for their title aspirations.As it turned out, City turned in quite a masterful performance and at this time of writing, they are still unbeaten in all competitions this season, even with a few penalty shoot-out scares along the way.One man that has been instrumental since his £50 million move in the summer is Kyle Walker.Eyebrows were raised at the fee City paid for the former Tottenham man, but Walker has excelled in making City a more dynamic attacking force and mobile defensive unit.Now, new footage has been released showing Walker completely mugging off a Manchester United ballboy during the 2-1 victory. If City fans didn't already love him, they sure will now!Speaking after the dust has settled, Jose Mourinho believed the tunnel bust-up was as a result of different 'education'.“The only thing I can say is that for me it was just a question of diversity, a diversity in behaviours, diversity in education, just that and nothing more than that”However, Guardiola explained: “We were inside [the changing room], it is normal,” Guardiola said. “We didn’t do anything exceptional, we did what we did in the past and what we will do in the future.“The image can speak for itself. What happened after the game, it was a normal celebration.“I am the guy who encouraged them to celebrate between each other. And that is what we did. And after what happened, hopefully it cannot happen again.”Either way, Walker set the tone! City fans obviously loved it, United fans... not so much.