Reading sealed their place in the 4th Round of the Cup with a thrilling 5-2 victory over the Terriers on Tuesday night and the star of the show for the Royals was striker Vydra, who scored a second-half hat-trick.
McDermott was clearly pleased with Vydra's contribution on the night as the striker, who joined on loan from Watford in the summer, had netted just three goals prior.
McDermott said: "I just said to Matej to play with a smile on your face.
"If you miss chances, who cares? It's not an issue. You just keep doing what you're doing, you're working your socks off. You've never hidden.
"He tries his utmost every game. He's a good guy and I speak to him regularly. I was absolutely delighted for him tonight. The red card was a big moment in the game. Up to that point, it wasn't good from us. But at least we showed how to play against 10 men and I'm delighted we got through.
"We just didn't get going early on. We weren't right, we weren't at it. It's something we need to address. We know we have to be better than that."