The boss has again praised the young striker who has had to lead the Reds' attack in the absence of the injured Fernando Torres.
"I think he is doing well because everyone has been talking about Torres, so to play in his position, work hard and score goals is difficult," said Benitez.
"When people talk about Torres, you know the next striker will always be in a bad position.
"But Ngog is working very hard, he has good movement and technique, and is scoring goals. For a young player, you cannot expect any more from him.
"When we signed him, we were talking about him playing maybe five to 10 games a season, 15-20 maximum.
"Now he is playing a lot of games, which is very good for him and the team also.
"Sometimes for a young player it can be difficult because you have to fight with two strong centre-backs in difficult games.
"But he has scored some goals and has given us some options in attack. We are watching the progression of a very good young player.
"He likes to train and learn. We were doing training sessions with him and Torres and they were working together on some movements. He is someone who is keen to learn.
"Always when you talk about young players, you talk about the price, so when you put everything together, he is a very good signing."