Grealish, whose international future has been the subject of speculation in recent weeks due to the youngster's eligibility for both the Republic of Ireland and England, netted his first Premier League goal in Sunday's 3-2 reverse to Leicester City.
The midfielder celebrated his 20th birthday last Thursday, and rounded off his week with a curling effort from the edge of the box for his maiden strike in England's top division, and the youngster has caught the eye with his displays over the past six months.
Speaking to Sky Sports News, Sinclair, who ran out for England 12 times and appeared at the 2002 World Cup, believes that Grealish can eventually go on to represent the Three Lions - if he correctly channels the acclaim that comes with a burgeoning reputation in the Premier League.
Sinclair told Sky Sports News: “He’s an exciting player. He’s one of those that gets bums off seats in the stadium and he missed a chance against Leicester but he learned from that and curled another one into the corner.
“It was a great moment for him, his first goal in the Premier League as a young player. We all remember ours and obviously Tim Sherwood has had a hand in his development.
“Over the summer he made a few mistakes, but now he’s back and he’s fit. He’s an absolute athlete and he can do really well if he keeps his feet on the ground.”
However, speaking last week, England boss Roy Hodgson rejected claims that he would call up Grealish just to keep him out of the clutches of Martin O'Neil and Roy Keane at the Republic of Ireland.
"I would like him to come out and say, 'I've thought about it, I've got the two possibilities and I'm opting for England' and then he will be available for selection" said Hodgson.
"But he has been injured, to be fair, so he wouldn't have been selectable for any team during these September fixtures. Now maybe before the October fixtures he might make that decision."