The red card changed the game most definitely, but it shouldn't have had to. It was United who, instead of defending for their lifes and go for a counterattaking strategy, let two goals in. They should have fought like warriors defending their goal and use the injustice of the sending off to spur them into action. It's because United is not accustomed to be on the wrong end of bad reffering calls that in the end was their demise.