RUNAWAY Premier League leaders Manchester City opened up an eye-watering double-digit lead over rivals Manchester United after Nicolas Otamendi fired Pep Guardiola’s men to derby victory at Old Trafford.

The much-anticipated 175th Manchester derby was comfortably the biggest game of the Premier League season, such was the need for Jose Mourinho’s side to reduce the deficit. But the gap between table-topping City and second-placed United grew to 11 points when Otamendi volleyed home a second-half winner after Marcus Rashford cancelled out David Silva’s opener.

An untimely end to United’s club record-equalling 40-match unbeaten home run strengthens their rivals’ grip on the title after just 16 matches – of which they have won the last 14 in a row. That is a new top-flight record run within the same season and an outcome that looked likely after Silva gave City a deserved first-half lead, with the playmaker capitalising on a corner that had deflected off Romelu Lukaku.

United fortuitously went into the break level after Rashford seized on a Fabian Delph mistake, but the blue half of the city were not to be denied as Lukaku’s hashed clearance allowed Otamendi to volley home early in the second half. Ander Herrera was booked for diving in the box and Ederson Moraes produced an outstanding double save as the hosts tried to snatch a draw, but City move on to 46 points as a result of a victory that leaves Mourinho’s men reeling.

However, the Portuguese said his side will continue to fight to catch City. He said: “They are a very good team. I think they are lucky, they had all the decisions in their favour.

“Of course, their advantage is a very good one, but Tuesday is another day in the Premier League and I am pretty sure all of us, us in second, Chelsea in third, and those in fourth and fifth and sixth, everyone is going to try to fight for points and try and reduce the distance.

Mourinho claimed his side were denied a certain penalty when Herrera went down under a challenge from Otamendi, with referee Michael Oliver booking the United player for diving.

“I am sorry for us and sorry for Michael, I think he had a good performance,” Mourinho said. “The referee had a good match but he made one mistake and his mistake was crucial to the outcome of the match. Last season we had a similar situation here against Man City. We were winning 2-1 and Mr Clattenburg didn’t see the penalty – Claudio Bravo on Wayne Rooney – and this one also.”

Guardiola responded: “Last season it was the same, we won here and the comments were about the referee. And today we have won and the comments are the same. We are an honest team. We want to play and we did it. We came here to play. Wow, we played outstanding. To play here at Old Trafford and play the way we played with the ball and trying to be patient, it was so, so clever.

“We are so happy because it was an important game for us and at our rivals, so big credit to the players.

“I am happy, and this style of play – we can do it in England. People have said the way we tried to play at Barcelona is not possible in England, but it is always possible to play football, keep the ball and we did it.

“I always believed that we could do that. Anybody can play the way they want and that is why football is beautiful. I am happy to go to places like Stamford Bridge and Old Trafford and against contenders, we have beaten them. In December it is impossible to be champions but that gap is very good for us.”