The Coventry City boss has been discussing the Newcastle youngster's 'footballing brain.'
And no wonder following the 18-year-old's second brace in as many games.
But Mowbray hasn't simply lauded the Magpies youngster in any sort of generic terms. No, the Coventry boss has explained a quality of Armstrong's that is very rare indeed for a striker so young and inexperienced.
Indeed, after watching his side beat Millwall 4-0 in League One on Saturday afternoon, Mowbray told reporters: "Armstrong needs a lot of credit for the opening goal. Two minutes earlier the keeper had come steaming out of his box, playing like a sweeper - I’m assuming they thought he needed to help out the central defenders because Armstrong is so fast - but when he got the ball he didn’t even look; he knew the keeper was going to be on the edge of his box.
"That just shows his quality, playing the football match in his brain."
There is, understandably, little doubt as to Armstrong's talent among Newcastle fans - and now the Coventry faithful.
The 18-year-old's pace is also undeniable. But what Mowbray's comments highlight is an intelligence beyond his years. Too many Newcastle players over the years have failed to show any sort of footballing brain regardless of their age.
But, as a teenager, Armstrong is clearly demonstrating an instinct and ability to think rapidly on his feet.
It is only in League One, granted, but this boy looks like he can become a Newcastle superstar one day as long as he doesn't get carried away.