Lampard will have the task of stopping the playmaker when Aston Villa visit Stamford Bridge on Wednesday.
"I think he's doing it," Lampard said of Grealish putting himself in the debate for a Three Lions call-up. "He's playing at a level now where he is obviously forcing himself into the argument. It'll probably be a matter of time.
"I never want to tell Gareth what to do but his performances at the moment of a really high level. He's a big threat for us and a fantastic player. His game has really come on. He is a joy to watch when he's not against you because he moves so well with the ball. He's a really good player."