The 22-year-old netted 13 times in the Bundesliga last term, helping the Red Bulls to a second consecutive season of European football.
As a result, Werner has made the provisional Germany World Cup squad and has been linked with the likes of Manchester United.
"To become a world-class player, I'll probably have to play in an even better team at club level," Werner told Goal.com. "I still have four or five years to learn, and then to become world class.
"I want to be honest, Naby Keita has not become world class with us either, he may now be with Liverpool. To become world class, you have to play big games, such as the final or semi-final of the Champions League."
Werner joined Leipzig from Stuttgart in 2016 and has scored 44 goals in 72 appearances.