Danny Welbeck scored United's second with a powerful volley in the 30th minute
Manchester City 2-3 Manchester United
Manchester United held off a spirited display by 10-man Manchester City to win an enthralling FA Cup third-round encounter at the Etihad Stadium.
Wayne Rooney put the Barclays Premier League champions in front in the ninth minute before Vincent Kompany was sent off for a dangerous tackle on Nani in the 12th minute.
Danny Welbeck extended the visitors' lead before Rooney added his second as United took to a 3-0 lead into the half-time interval.
But despite their numerical disdavantage, City hit back after the break with goals from Aleksandar Kolarov and Sergio Aguero to set up a thrilling finish.
Kolarov went close with a free-kick in injury time but United, who introduced Paul Scholes as a substitute in the second half, held on to book their place in the fourth-round draw.
