Mowatt was handed his debut against hometown club Doncaster in August after progressing through the club's academy and has gone on to make 13 appearances for McDermott's side.
The 18-year-old has started in Leeds' last five matches and signed a new three-and-a-half year contract earlier this month.
"He's taken to it seamlessly quite frankly and he's going to get better because he's young and he's going to mature," said McDermott.
"He's going to mature into a real quality player. The one thing with Alex is that he's level-headed, he keeps his feet on the ground.
"He's really grounded and he wants to do well. He trains really hard and he prepares himself every day to the best of his ability."