Bendtner, who joined Forest on a free transfer earlier this month, struggled to establish himself under Wenger in nine years at Arsenal and is set to face his old club in the third round of the League Cup later on Tuesday.
Bendtner made just 83 starts under Wenger but the Frenchman felt the Danish international has all the qualities to succeed at former European champions Forest.
"It was a surprise to me that Nicklas signed for Nottingham Forest, but at some stage he needs to restart his career," Wenger told Arsenal's website (www.arsenal.com).
"Sometimes when you are a player of his quality, you just need an opportunity. We know he is a top-quality player, but he needs to play.
"Of course he has a point to prove. He's playing at a level 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 humble enough and focused enough to show he can fight again."
The 28-year-old Bendtner, who also had loan spells with Sunderland, Birmingham City and Juventus, said though he spent nearly a decade with the London club, it felt like a "distant memory".
"(Arsenal) feels like a long time away. I had been there a long time but so much has happened since, so it's a little bit of a distant memory," he told BBC Radio Nottingham.
"Things happen in football, it's a quick career and you have 15 or 20 years.
"I was there at an early age and there's many things -- ups and downs -- that have happened but it's in the past and I only look to the future."