I understand that Mancini didnt want to take chances, after the red card Roma werent back out they would be attacking cause the game was already lost for them, Mancini did te right thing imo, it's sometimes better to be cautious than reckless by taking chances, after all Roma are the best attacking team in the league, if we were exposed at the back for a second they'd have killed us with counters of thei extremely fast FWs.
Only if we drawed or lost this game people would have raped Mancini for chosing to defend with man up.