Rush told Sky Sports: "I'm delighted with what Steve has done and I think he's happy here.
"I would be very resistant if anyone came knocking and I wouldn't advise them to.
"He's only been here for a few months and I was sure he'd be successful. I'm looking forward to working with him long into the future.
"He's at the start of his project here and he's looking forward to get cracking with a big summer. It will be his first pre-season at Derby."
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