Fabregas's injury had critics writing off Arsenal's chances of overturning the first leg deficit and then Nasri showed, possibly for the first time in his Arsenal career, what all the fuss was about in France.
Allowed to play in his favoured position in midfield, as opposed to the wing where his contribution has been lacking, the Frenchman ran the game.
His pace, energy and eye for a pass created the first goal when he fed a through ball for Arshavin, it spilled away from Porto's keeper Helton and Bendtner only needed to apply the finish to get the first of his hat-trick.
Nasri then buzzed around the field, harrying the opposition when Porto were in possession and driving Arsenal forward when he had the ball.
Just five minutes in the second half sum up this captivating display. Defending against a corner, Nasri on the line repels a certain goal from a driven header by Cristian Rodriguez.
Then he went up the other end and with seemingly nothing on, the midfielder bravely drove at the Porto defence. From a standing start, he took on one, two, then three defenders before smashing the ball past the helpless keeper with a perfect far-post finish.
That was 3-0 for Arsenal and the game was now out of Porto's reach.
Nasri's work for the night was done and Wenger substituted him just a few minutes later.
The Arsenal faithful applauded their new hero. Who knows how long Cesc Fabregas will now be out injured; but on the basis of this display, he won't be missed quite as much as once feared. His only worry will be having to move back out onto the wing once Fabregas returns to the starting line-up.
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