The 22-year-old Cambridge City player featured for 75 minutes of the 0-0 pre-season friendly draw with Torquay at Plainmoor.
Clough is keen to bring in players who will be immediately in contention for a first-team berth and admitted Neilsen is not yet at that standard.
"Scott did OK and we will probably monitor his progress," he told the Derby Evening Telegraph.
"He certainly did not look out of place coming into the team and in training.
"I think at the moment if we are going to get anybody, ideally we want them to be challenging for a place in the first-team squad.
"We have got the development squad and we could still do with adding one or two to that but Cambridge will want a fee for him and we are not in the market for that at the moment."
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