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The German striker agreed a €50 million ($NZ88 million) move to Stamford Bridge last month and has already started training with the Premier League club even though he is not eligible to play until next season.
Werner (24) made the move after helping Leipzig finish third in the Bundesliga with 28 goals and said his discussions with Lampard over how he would fit into the Chelsea side convinced him to sign for the Premier League club.
"He [Lampard] was the main point. We talked a lot about things like system, like how he wants to play and sees me playing, and how the system fits to me," Werner told the club website.
"He's a really nice guy who not only told me what he wants from me as a player because he wants to help me."
Werner said that he always had the ambition to play at a "big club" like Chelsea and that the English top-flight was the right destination for him.
"The style of the Premier League is very fast and my speciality is that I am really fast so I think it is perfect for me to play here," he added.
"It is another league in another country so I can improve myself to bring it to another level."