"Here's a kid who won the Tour of California a couple of months ago and is sitting in 10th. When there was the selection on Cat Mountain - Mont du Chat - he was there.
"He looked good to me."
Bennett entered this Tour de France with modest expectations, hoping to steal a stage win, if the opportunity arose.
Now, halfway through the journey, he has had to reassess that goal, with a high placing in general classification a realistic prospect. He currently sits three minutes 53 seconds behind three-time tour winner and race leader Chris Froome.
"Obviously, guys like Chris Froome can't ride forever," said Armstrong. "But kids like Simon Yates, Adam Yates and George Bennett - oddly enough, three Anglos - they're going to be factors and potential Tour winners in the future."
Armstrong wouldn't even discount Bennett as a force over the next 10 stages.
"We were talking about how great and strong and safe Chris Froome is, but 10th place is less than four minutes behind," he said.
"Four minutes isn't a lot of time - anything can happen."