The manager failed to get the best out of the flamboyant Dane during nine years at the Gunners, and the pair will come face-to-face again in the League Cup
Ahead of Arsenal's League Cup tie with Nottingham Forest, Arsene Wenger says he was surprised to see Nicklas Bendtner sign a two-year deal at the City Ground.
Bendtner spent nine years at Arsenal, making 171 appearances without ever doing enough to fulfil his self-proclaimed wish to be the best striker in the world.
Released in 2014, Bendtner had a brief spell in the Bundesliga with Wolfsburg, before arriving at Forest earlier this month.
And with the 28-year-old set for a showdown with his former employers on Tuesday, Wenger admits Forest's capture of the Denmark international raised an eyebrow.
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"It was a surprise to me that Nicklas signed for Nottingham Forest, but at some stage Nicklas needs to restart his career," Wenger said.
"Of course he has a point to prove - he's playing at a level where he is not used to. But he did start his career at this level at Birmingham City with Steve Bruce, where he did very well. Nicklas is focused enough to show he can fight again.
"You have to adapt and we are in a job when we have to show we are able to put our effort in everywhere and compete. Sometimes when you are a player of his quality, you just need an opportunity. We know his qualities and he is a top quality player, but he needs to play.
"The perceptions people have of him is that he is over confident but I don't think so. He was sometimes impatient when he was with us. He was disappointed not to get the chance and you can understand that.
"I am not here to judge people. Sometimes you manage to get it and sometimes we do not find the key. Then you have to leave the key to someone else who has the potential to find it. Nicklas could explain much better than I can about his career."