The youngster was the final goalscorer in the 6-0 win.
Klopp told the club's website: "It is just so nice. Not only the goal, but when you see the situations when he came on, I think the first pass was between the two strikers, he got it in the No.6 position where he is calm, turns and passes the ball out. We can teach the boys a lot, but they have to bring a lot. Obviously the basis for Leighton is not too bad and Jake [Cain] did really well, as well. All of the boys.
"For Sepp [Van den Berg] it is always hard for centre-halves. We have four, so sitting outside [but] he looks really promising in training sessions. Ki-Jana, centre-half and right-back and looks really good. You see them – when Harvey [Elliott], Curtis [Jones] and Neco [Williams] played, it looked good as well. It's coming, it's nice and nice they are here and training with us.
"The way we play helps the players to feel safe; everybody is defending and you should never feel alone in a big area where you have no chance to sort the situation. That's what I really like and for the boys it was really good. Yasser [Larouci], too, he looked really good – so that was good and very important for us."