The 20-year-old net his fifth goal in six second-string outings in victory over Chelsea this week.
"Conor looks lively, he looks positive when he gets the ball, looks a real threat to opposition defences and he puts defenders on the back foot, which from a forward's point of view is a great thing to do," Stubbs told evertonfc.com. "From a defender's point of view, trust me, it's not great when strikers do that.
"I think he's back to where he was before he had all his injuries and he's doing great at the moment. I'm really pleased for him."