The Danish striker appeared in a Forest shirt for the first time from kick-off in the Championship club's 4-0 loss to Arsenal in the EFL Cup at the City Ground on Tuesday night.
Bendtner, who spent almost a decade with the Gunners, had some decent moments when setting up Pajtim Kasami while shooting just wide of goal early in the second half and his overall display was something that pleased Montanier who felt his entire side would have learned a valuable lesson from playing against Arsene Wenger's men.
"Like the team he started very well at the beginning and then after it was very difficult for him because Arsenal had the ball and he did not have a lot of opportunity to play," he said.
"But physically I am surprised he is so fit because he had not a big pre-season with Copenhagen.
"It was a good experience not only for Nicklas but for all the players because Arsenal have great technique, better than us, and it was difficult for us but my players, they gave everything."