The Scottish striker scored his 15th Championship goal of the season in Saturday's 3-3 draw with Watford prompting McDermott to play down claims that he could be on his way to the Premier League next month.
"I don't think this is a selling club any more. We got offered a certain amount of money for Ross in August and I don't think that would buy a part of his body now," he said.
"He's not even at his peak yet. He'll get better and better. He was bright and vibrant and he makes things happen. We need the big players to come up with the goods."
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