De Gea as Messi pounced, although the offside flag was raised in any case. Yet United finished the first half strongly, with Danny Welbeck defending well from the front and Scholes at his probing best. Ashley Young's inswinging corner almost caught Valdes out with Nemanja Vidic and Rooney unable to scramble in the rebound and Nani earned a penalty after being caught by Tello's careless tackle inside the box. With the clock ticking over into injury time, Rooney stepped up but saw Valdes parry out his spot-kick and the United striker slashed the rebound well wide with the goal gaping.
Undeterred, Sir Alex's side started the second period in impressive fashion with Valencia bursting forward to find Welbeck, who teed up substitute Shinji Kagawa for what was almost a dramatic introduction to the game but Jose Manuel Pinto, another half-time replacement, dived to save. Kagawa tested Pinto's reflexes again soon afterwards with a cross-shot but Barca passed their way back into the ascendancy.
Thankfully, De Gea was in top form as he kept out Dani Alves, although the Brazilian was offside as he latched onto Cesc Fabregas' slide-rule pass, before pulling off two wonderful stops in quick succession. The former Atletico Madrid No1 stood up well to Alexis Sanchez to win a one-on-one with the Chilean and then dived full length to tip a Pedro header around a post.
Back came United with Nani unable to profit after being gifted the ball by Pinto and playing a one-two with Kagawa, as Marc Bartra nudged him to the ground inside the box, and the Portuguese winger was then booked, along with Busquets, after a flare-up after being tugged back when sprinting forward.
More substitutions interrupted the flow of the game and penalties appeared increasingly inevitable although Nick Powell and Scott Wootton came off the bench for the best experience of their fledgling careers.