The European Cup winner feels that Grealish, as well as Everton midfielder Ross Barkley, has the ability to follow in the footsteps of the likes of George Best and David Beckham if he learns to keep his head straight.
When asked who could become the next England superstar, in an interview by sc.qa, Keegan said: "The only way to be a superstar is to play really well every week and be successful. The first superstar in England was George Best, who was an absolute genius.
"I followed and by the time David Beckham came along there was a different procedure. The media was much stronger and everything was much more magnified.
"Ross Barkley is another candidate."