Bruce, who was involved in an exchange with some Arsenal supporters behind the dugout during the closing stages, was Bendtner's manager when the striker was on a loan spell at Birmingham and then at Sunderland.
"He is a good football player for the size of him. I hope that sooner or later he really knuckles down and really makes a go of his career because he's a very, very good player, but the mentality of Nicklas is always what everybody questions," said Bruce.
"He's a big, strong, powerful centre-forward who's good in the air and has good feet for the size of him. He's got the lot really, if he wants it - but there's always a 'but'."
Bruce added: "Did we try to sign him in the summer? We were having a look, but the level of salary was always going to be a problem for us.
"Nicklas is a good boy, he has always done well for me and it was Sod's Law he would do that against us today.
"When was the last time he scored? It was for me (at Sunderland) wasn't it? Well, there you go."
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