Slot handed the former Chelsea winger a senior debut last season and is pleased with what he's seen from the 17 year-old this month.
Advertisement
Advertisement
Ngumoha scored in Liverpool's friendly win against Yokohama F Marinos on Wednesday.
"Rio again showed the quality he has," said Slot.
"That is nice for us because we have a lot of very good players but to get some brand new players from the academy is helpful. It gives energy to the team.
"It is nice to see young players at 16, 17 or 18 impact the game. But there was also a moment in the game where he should have squared it to Curtis (Jones). But if you are 16 and you can impact games like he did, that is definitely a compliment."