The midfielder, 19, penned a contract extension until 2018 at Villa Park on Tuesday.
Lambert believes that the youngster can go on to become one of the teams's brightest players after committing his future to the Villans.
"There's always an excitement around a young player who comes through the academy, but the thing is the potential we have signed in Jack Grealish is great for everyone connected with Villa," the Scot told the club's official website.
"He has a long way to go in the game but the potential that's in him, we believe, means we could have a really good player in the years to come. We believe Jack can be a really good player for Villa and that's very encouraging in terms of where we see our future."
Grealish has made five appearances in all competitions for Villa so far this season.