The first two goals for Barca came from a lack of marking. No-one followed Pedro into the box for the first and Messi was given 5 yards when he received the ball to score the second. I think if United had closed down quicker and had someone to specifically mark Messi, those goals could have been prevented. Everytime United got the ball, Barca were all over them and most of the time, they only had time for one touch. It was because United were chasing the game that Barca got the 3rd.