Werner left Leipzig for Chelsea in the summer.
His former coach is also very ambitious, and may want to coach in the Premier League one day.
Nagelsmann admitted to talking about the subject with Werner.
Asked about the two leagues, he told reporters: "I've never been a manager or a player in the Premier League, so I could not compare it in detail to the Bundesliga.
"But when I watch games of the Premier League I recognise that it's a very tough and good league.
"So perhaps it's one of the best leagues in the world, I think that's clear, but perhaps it's the best league in the world.
"But if I will be in the Premier League in the future, perhaps then I could compare it a bit more in detail and then you can ask me the question again and I will answer in a bit more detail."