Edin Dzeko and Anderson both earned bookings after they were involved in a shoving match following a late challenge by the Bosnian.
Barely a minute later, Micah Richards lunged in on Ashley Young and was perhaps lucky to escape with only a yellow card. Wayne Rooney couldn't inflict further punishment; his free-kick whizzed just over the crossbar.
Welbeck and Nani then combined to unlock the City defence, although Welbeck's final ball across goal was cut out by a Blues defender. The young striker then headed tamely into Joe Hart's arms as United looked to turn early dominance into goals.
A number of niggly fouls disrupted the game's flow around the half-hour mark and fuelled the already hot atmosphere inside the stadium. One infringement resulted in a United free-kick 30 yards from goal, which almost made its way into the bottom corner via a deflection off the end of the Blues' wall. Another handed City the lead on 38 minutes.
It was David Silva's teasing left-footed delivery from the right wing that did the damage. It curled over Vidic but in front of Rio Ferdinand, into an area where Joleon Lescott soared high to head past David De Gea from six yards.
The Spanish goalkeeper's debut got worse in first-half injury time when a dipping Dzeko shot from distance deceived the 20-year-old and doubled City's lead. The ball was struck with some venom, but it was its late movement in the air that caught the former Atletico Madrid man by surprise.
So, after a bright start and plenty of early promise, Sir Alex's men found themselves, somewhat harshly, two goals behind at the break. The boss