Manchester City manager Pep Guardiola has insisted that there is "no doubt" about the quality of Manchester United counterpart Jose Mourinho.

Mourinho's future at Old Trafford has been called into question during the opening stages of the new Premier League season following the club's worst start to a campaign since 1992-93, in addition to reports of unrest behind the scenes.

The three-time Premier League winner has repeatedly highlighted his past achievements to counteract the criticism in the wake of United's 3-0 home defeat to Tottenham Hotspur on Monday night, and Guardiola has leapt to the defence of his cross-city rival.

"I said many times I don't judge. Of course we are judged for the titles we get now, especially if you have won titles as it can work. There is no doubt about his quality - I have never doubted that in the past, I won't now. But it is not only the titles," Guardiola told reporters.

"I have said many times, for example with myself, I have won at amazing clubs with amazing players, but if that had not happened I would not have won titles. But there are many many managers who don't win titles who are excellent. That's why on one side it happens because you have something special to win titles but the other side managers are so good it is not necessary to win because good clubs, good players sustain you.

"In many circumstances, the manager cannot control it. That does not mean they are not good. Our [a manager's] position is results, but with every manager it is what he believes, what he likes, tries to get results in his own style and the way he trains.

"Only the players know exactly how you are as a manager because they see you every day there. They know they have more information than the rest of the world, the fans the media and everybody. Only the players know exactly who we are and normally even with the players we are judged, if they play we are good, if he doesn't play the manager is not good. It's simple like that."

Guardiola frequently clashed with Mourinho during their time in charge of Barcelona and Real Madrid respectively.