I think if Arshavin have gone down immediately when Bramble pushed him, Arsenal would have gotten the penalty. For the offside call, it was pretty marginal. Arsenal should have gotten the benefit of the doubt from the linesman there.
And oh, the referee for the Arsenal is apparently from Manchester.
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Here's another interview. This time, it's with Jamie Carragher. A great one too.
Jamie Carragher exclusive: What the Liverpool defender really thinks of Fergie, Neville and United | Mail Online
The main reason why Arshavin did not go down quickly was because Bramble pulled his trouser and Arshavin had to guard it.