Manchester United defender Rio Ferdinand suffers facial injuries after being struck by coin thrown from the crowd Ferdinand was able to complete the game and afterwards on Twitter said: "Whoever threw that coin, what a shot! Can't believe it was a copper 2p....could have at least been a £1 coin! Sir Alex Ferguson adopted a more serious tone. "It was disappointing when the supporter ran on the pitch and Rio got hit in the eye by a coin," said the United manager. The game didn't deserve that. It was a sad postscript to a thrilling afternoon in which United thought they had established a match-winning lead through Wayne Rooney's double before City hit back in the second half. Indeed, once Pablo Zabaleta had levelled after Yaya Toure had halved the deficit, it seemed like the hosts would go on to win, only for Robin van Persie's deflected free-kick to seal the spoils for United, who move six points clear at the top. "We should have been out of sight with the chances we had," said Ferguson. But you have to give credit to City. They keep going and they score late goals and they have done it against us again today. Fortunately we got the last one. Rooney's double established him as United's leading scorer in Manchester derbies. The England man is now level with City duo Francis Lee and Joe Hayes on 10. However, when Ashley Young had a third incorrectly ruled out for offside, City took advantage almost immediately, leaving the game on a knife-edge. "Intensity, passion, competitiveness...everything was there," Ferguson said. The incident with Ashley was disappointing because from 3-0 up it went to 2-1 in minutes. Football can kick you in the teeth that way. But there will always be controversy in a match like that because there are so many things happening. It left Roberto Mancini to reflect on another dismal performance from Mario Balotelli. The Italian was preferred to Carlos Tevez but after an ineffective opening period, showed no sign of improvement immediately afterward, triggering a stark warning from his manager. "I love Mario but it is important for him to start to think about his job," said Mancini. He has everything to play well but he can't continue to play like today. We wanted more from him. When you have a player that has Mario's quality, you cannot understand why he continues to throw it out of the window. It is incredible. I have seen players in my life with fantastic quality. But in the end, they did nothing. I don't want Mario to finish like these players. It would be bad for him.