Brobbey is set to join the Bundesliga title chasers on a four-year deal at the end of this season after rejecting a new contract at Ajax Amsterdam.
The 19-year-old only made a breakthrough into the Ajax first team this season but has struck four times from 11 appearances across all competitions.
Leipzig fans are curious what they will be getting from the Netherlands youth international, who is of Ghanaian descent, but Nagelsmann has moved swiftly to play down expectations from the striker despite drawing similarities between him and the highly rated Inter Milan forward.
"It is always very tough for a player when you compare him to others as people start to grow expectations that are not good for a player at that age," Nagelsmann told reporters.
"In regards to his physique and the way he plays, he is similar to Romelu Lukaku. And we would be happy if he can manage to become a player with the same qualities. But to paint a picture for the fans, you can definitely say that he is similar to Lukaku. But it is a great wish of ours that he can develop himself in a similar way and that he will be able to become as important for European football [as Lukaku].
"If that will be the case, then our scouting department has made a great decision. We will cross our fingers for that to happen. But please don't start saying that he will play just like Lukaku, because this won't be the case."
