The Uruguayan striker has been biding his time on the bench for most of this season.
However, Nunez came off the bench to great effect recently, helping the Reds beat Brentford with two late goals in their Premier League contest.
Slot told reporters on Darwin: “I think the most difficult (thing) in football for a team, but also for an individual, is to find consistency. Only a few players in the world are able to be at the same level every three days in a row.
“And then there’s a big, big, big group of players that are able to play very well many times but not every single time – I think he is one of the players that belongs to the group that is good many, many, many times. The next step for him – it would be nice – (is) if he can go into the bracket of the five, six, seven or eight players in the world that are every three days outstanding. I do know we have also a few players that are every three days of a very high standard. It’s a nice challenge for him to go to that group of players as well.”