The 24-year old striker, who is back at Tannadice on loan from Blackburn Rovers, netted in the 33rd, 45th and 91st minute of the Terrors' comfortable victory which pleased his boss to no end.
"I never doubted he was capable of that," McNamara said. "I'm delighted for him. I hope scoring three goals can be a turning point for him.
"There's been a lot of pressure on him to come up here and perform.
"Hopefully the other boys - like Nadir (Cifti), Armstrong and Gauld - chipping in with goals has taken a bit of weight off his shoulder and the goals will come. I hope there's more to come."