Napoli coach Benitez has declared his admiration for the Belgium international, who endured a disappointing first season at Old Trafford.
The Spaniard is monitoring Fellaini's situation at the Premier League club, with new United boss Louis van Gaal set to make a decision on the futures of several players following their tour of the United States.
And on Tuesday, Benitez stated that Napoli can do no more than bide their time as they wait to discover if the former Everton man will be made available for transfer.
"We cannot discuss the market, we have so many players being named in the newspapers. I work with what I have. Everyone is working to improve in condition and in play," the Spaniard said.
"Fellaini is a Manchester United player, it does not depend on us, but it depends on them.
"He is a great player, but he is at another team. It appears he is waiting for Van Gaal. We will have to wait.
"Is he the right player? We have players that work very well, whilst it also depends on who leaves. It is not easy to name names.
"What features in a midfielder am I after? Players who have the mindset to win every game, then we can start to talk about the technical quality.
"With our same mentality, but with a little more quality."
