Werner agreed a €50million move to Stamford Bridge last month.
The 24-year-old has already started training with the Blues, even though he is not eligible to play until next season.
He made the move after scoring 28 times to help Leipzig finish third in the Bundesliga and he has now said his discussions with Lampard 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’s website.
