Manchester United moved six points clear of Chelsea after beating the Blues 2-1 at Old Trafford on Sunday.United's top four prospects are now looking rosy while Chelsea boss Antonio Conte was forced to admit Chelsea could be trouble following their loss in Manchester.The battle between United and Chelsea has always been intriguing, but the fact that Jose Mourinho used to be a very successful manager of Chelsea and is now in the Red Devils' dugout has provided another wrinkle to the rivalry.Mourinho got the better of his Italian adversary on Sunday, but both men did shake hands before and after the game despite a long-running war of words in the media.On the pitch. though, it was Chelsea who took the lead in the crunch clash when Willian burst through after a lovely ball from Eden Hazard.The Brazilian powered an effort beyond David de Gea and Hazard looked like he would be a real handful for the United backline.However, in the 73rd minute with the score level at 1-1, Conte chose to substitute Hazard - who didn't appear injured - and replace him with Pedro.Just two minutes later, Jesse Lingard netted the winner for United and Mourinho's men would see the game out to grab three precious points.After the game, Conte explained his decision and the like-for-like switch appears to be tactical.“It was a tactical decision,” he said. “We have to keep the same performance for 90 minutes. Otherwise we don’t have a great balance. Every single player has to work with the ball, without the ball, otherwise we lose our balance and the game.”Was Hazard not running hard? Unsurprisingly, Chelsea fans aren't buying his explanation and they weren't happy with the decision.

One man who was happy after the game, though, was Mourinho. The ex-Chelsea boss couldn't hide his delight at the result.

“I think we beat a fantastic team. For some reason, they were the champions last season. For some reason, they played the way they did against Barcelona. For some reason, they started the game so well as they started here.

"We beat a very good team and to beat a very good team, you need to be organised but you also need to have a humble spirit where everybody works, everybody fights, everybody tries to follow a game plan. I repeat, we beat a very good team.”