"Sidwell is a good all-round midfielder," said Wenger of the 26-year-old he allowed to leave in 2003.
"He is good defending, a hard defender and goes into the box well. He is a bit similar to (Frank) Lampard in his game. I'm happy he has had a good career because we always knew he would make a professional.
"It was difficult to assess at what level [he would play] because when he was younger he had technical problems but he has improved that side of his game and is now a very good player."
Having watched his development from afar, Wenger could be forgiven for regretting Sidwell's departure but he said: "You can only play with 11, it's as simple as that.
"The best 11 play and at the time he was not within that. Even in the squad, it was difficult for him to get on the bench.
"At some stage, for his development, it was better for him to go and play somewhere. We don't forget - if you look at players educated here at Arsenal Football Club you will see we have produced many good players."