Alot of people have villified Wenger for selling Samir Nasri, and to a rival no less. They say it was the wrong decision because he was one of their best midfielders and was an asset to the team.
But what most of those people may not understand is that Wenger played that whole situation masterfully.
Nasri was on the last year of his contract and was not about to sign a new one. His value had gone up considerably since Wenger bought the Frenchman from Marseille in the summer of 2008 for £12m.
Given this, if Wenger had kept Nasri as his critics said he should, he'd have walked away in a year's time for nothing.
Wenger wisely named Nasri for his Champions League squad in the qualification round against Udinese, as Manchester City stalled on bidding for him. This decision made Manchester City expedite their offer, fearing Wenger would field Nasri, thereby cup-tying him—which would prevent him from playing in the CL for any other club until the knock-out stages in January.
In the end, Wenger made about £25m on Nasri's sale—over twice what he paid for him just three years before. Not bad business at all!