Reports in the summer criticised the Blues for lacking a creative spark in midfield, but Lampard believes that 23-year-old Mata has now addressed that problem.
"[Mata] has definitely added a lovely dimension to our team," said the England midfielder.
"We had a very good unit but it's great to have someone with his sort of jinky creative ability that can offer something else.
"Juan's a little bit like Silva at Man City. He's got that similar quality and that is only going to improve us."
Mata and Silva were former teammates at Spanish club Valencia.