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If AC Milan are to progress, it could well be down to their main man Zlatan Ibrahimovic.
The striker's positioning, movement and awareness caught the Barcelona defence out in the first half at the San Siro, and going back to the Camp Nou, the former Barca forward will undoubtedly be fired up to go one better.
His diagonal run to meet a through ball and cut into the opposition defence left him with a great chance to score.
And his positioning and awareness to make a great key pass for Kevin-Prince Boateng proved not just what he can do with time on the ball, but also the unpredictability of his game.
The last time Barca played a tall, strong, fired up, unpredictable striker, they lost 3-2 to CA Osasuna.
Dejan Lekic, a player in the mould of Ibrahimovic, scored twice for Los Rojillos.
And considering they'll now be up against possibly the best tall, strong, unpredictable and inevitably fired-up striker in world football right now, there's a chance the big Swede will make a big difference.