The forward has scored 12 goals and registered four assists in 35 league appearances since being signed from Portuguese club Benfica last year for an initial fee of 75 million euros.
After struggling in front of goal in his debut campaign at the club, Nunez has netted three goals and provided one assist in his six league appearances so far this season.
He also had a goal and an assist in Liverpool's 3-1 win over LASK in the Europa League on Thursday.
"Massive steps in the last few weeks. He is a threat," Klopp said.
"He was always available for us; it is super-important for us that we have now – I am not sure it's the right word – a ball player.
"The defensive work he puts in now, that's probably the main difference. He always wanted, but it was less coordinated. Now that looks much better and we found a way how we can do it around him."
Liverpool are unbeaten in their league and are in second place, two points behind Manchester City. They next host Championship side Leicester City in the League Cup on Wednesday, followed by a league visit to fourth-placed Tottenham Hotspur on Saturday.
