José Mourinho was left disappointed by a derby defeat the Manchester United manager believes was borne out of a poor first-half display and some refereeing mistakes.

Old Trafford was the focus of the sporting world on Saturday lunchtime as city rivalries resumed and managerial hostilities renewed, having fought an at times ugly battle with Pep Guardiola for LaLiga glory.

Now they share a city and the desire for Premier League success, with Guardiola striking the first blow as Kevin De Bruyne and Kelechi Iheanacho’s first-half goals proved enough for Manchester City to leave Old Trafford with a 2-1 win.

Zlatan Ibrahimovic pulled one back before the break after capitalising on a mistake by debutant Claudio Bravo, who Mourinho felt should have been sent off for lunging at Wayne Rooney after turning into danger.

The United boss also felt Nicolas Otamendi should have been pulled up for a handball — decisions by referee Mark Clattenburg that compounded a poor opening period by United.

Asked if he was disappointed by the first half or encouraged by the second, Mourinho said: “Both. I think in the first half we deserved to be losing and in the second half we don’t deserve to be losing.

“The first half was their half and they got what they deserved. In the second half, we were the best team. We didn’t get what we deserve.

“Clearly disappointed with the first half, disappointed with some really poor individual performances that affect the overall performance of the team.

“And in the second half, very pleased with many things, disappointed with the result and disappointed two very important decisions from Mark that were against us.”

Initially coy when asked to elaborate on those decisions, Mourinho opened up on the decisions he felt cost United derby points.

“It’s obvious that is a penalty and red card to Bravo,” he said. “If it is outside the box, it is a direct free-kick and a red card. Inside the box, it is more difficult.

“It is more difficult because it is a big decision and sometimes the referees they are like us, they are human and they think twice before big decisions.

“Sometimes they don’t think twice and it’s a penalty and a red card, with a big possibility of 2-2 with a long time to go.

“In here (in the press conference), we will be speaking about a completely different story.

“The second penalty is Otamendi handball, which I believe that some of you will say ‘that’s not a penalty’. I say 100 per cent penalty because Otamendi tries to stop the cross in the face of the goal, but the cross comes behind him.

“He knows and he brings the second arm back. The first arm is the one that is close to his body. Clear penalty so we were punished by that.

“But we were also punished by our very bad first half and that’s football. And mistakes from the referee are football too.”

Jesse Lingard and Henrikh Mkhitaryan were brought in to the line-up for the derby, but replaced at half-time after poor displays.

Mourinho took responsibility for mistakes in the team set-up and, despite insisting they were not the only poor performers, suggested the duo could have come off sooner.

“I didn’t change after 20 minutes because I don’t want to destroy the players,” he said.

“I didn’t want to make three changes at half-time because I was afraid in long 45 minutes something happened.

“If it was a sport with a free number of changes and where the changes during the first half is something normal like basketball and all this kind of stuff, I would do after 20 minutes.

“But I did at half-time, we changed the direction of the game but we didn’t get the compensation I think we deserved in the second half.”