The German was asked about how new manager Arne Slot can hit the ground running next term.
While Hamann expects some drop off after Jurgen Klopp’s departure, he believes sorting out Nunez’s future is key to Slot having a productive first season.
Per The Mirror, Hamann said: "Liverpool have a very good team (but) I think there are still some doubts about Darwin. He (Slot) will need to make a decision there. Is he going to win you a league or a big title? I'm not too sure.
"I’ve always defended him, but I think it's gone too far now. I don’t think he’s delivered consistently enough in the two years he has been at the club."
Of Slot, Hamann added: "The people who know him, they speak very highly of him. He seems to be a man manager.
“From what I’ve read about him, there are similarities to (former Liverpool boss Jurgen) Klopp, which I think will help. At the same time, he can’t try and copy Jurgen – he has to be his own man."