The Partenopei currently trail Serie A leaders Juventus by 17 points and lost their Europa League last-16 first leg tie against Porto on Thursday after a solitary Jackson Martinez strike.
The disappointing season has not disheartened Benitez but he acknowledged that the Azzurri need to bring some new faces to San Paolo and also require existing stars such as Hamsik to give more to the club.
"We have many champions in our group and our goal must be to do better to attract others," the 53-year-old told Radio Kiss Kiss.
"If we grow as a team strong players will want to come to us. Napoli is missing a something, maybe even missing a leader. For sure that's the type of player that helps you win something."[Hamsik] needs to become a different player to who he was in the past. He must grow in terms of personality, now [Ezequiel] Lavezzi and [Edinson] Cavani, with whom he played great, are no longer at his side.
"He had a great start to the season, then paid something with the injury. But he has a chance to react and redeem himself."
Napoli director Riccardo Bigon revealed this week that the club are interested in bringing Porto pair Martinez and Juan Iturbe to Italy this summer, but Benitez remained tight-lipped on the prospect of signing the pair."I do not speak about players at the other teams," the former Liverpool coach said.
"And, in any case, I agree with the corporate philosophy to keep budgets in the black.
"We must try to secure second place, and therefore direct access Champions - it's a historic opportunity to attract new players so we can continue our path of growth."
Napoli, who travel to face Torino on Monday evening, sit third in Serie A with 55 points from 27 games, currently three behind Roma, who have a game in hand.