Louis van Gaal blamed himself for Manchester United finishing the game with 10 men , using all his substitutes before Michael Carrick came off as a precaution with a tight calf . The United boss said : ‘ It was of course an error from me that I give too much minutes to my substitutes . It is not so wise . 'Some players didn ’ t know that we were playing with 10 men because the crowd were yelling and it was difficult to get the message to them. ’ Manchester United manager Louis van Gaal ( right ) celebrates victory with Ander Herrera at full-time . An injured Michael Carrick walks along the touchline after coming off as a precaution with a tight calf . Aguero 's quick-fire ton . It will come as little consolation to Sergio Aguero that he reached the 100-goal mark faster than any player in Manchester City ’ s history with his double at Old Trafford . The striker has had to wait for that honour , however , with his first goal ending a barren run stretching back eight hours and 39 minutes to the defeat home to Barcelona in February . Sergio Aguero ( centre ) celebrates after scoring the opening goal at Old Trafford on Sunday afternoon . It was Aguero 's first goal since he scored for City against Barcelona at the Etihad back in February . Milner goes off in a strop . James Milner 's reaction to being substituted as he waited to come back on following treatment after a reckless challenge from Phil Jones does not augur well for the England winger ending his contract stalemate . Milner was standing on the touchline when he discovered that he was being replaced by Samir Nasri , and hurled an energy pouch to the floor in frustration before trudging back to the dugout . Manchester City 's James Milner goes off with an injury during Sunday 's Premier League derby . United felt that Martin Demichelis overreacted when he was caught in the face by a flailing arm from Marouane Fellaini in the second half , but the Belgian does have a rather patchy track record on that score . Pablo Zabaleta was furious that Fellaini was only given a yellow card at Old Trafford last season when he felt he was the victim of a blatant elbow from the United man . Manchester City 's Martin Demichelis ( centre ) protests to referee Mark Clattenburg as United players look on .
United finished the game with 10 men after Michael Carrick came off . Sergio Aguero reached the 100-goal mark faster than any other City player . James Milner hurled an energy pouch to the floor in frustration after he was replaced by Samir Nasri . United felt that Martin Demichelis overreacted when caught by a flailing arm from Marouane Fellaini .