Villa are at the foot of the Premier League table at the moment and are set to go down to the Championship at the end of the season.
Grealish, who is just 20 years of age and can play as a winger or as an attacking midfielder, is a very talented player, and Redknapp believes that he could be a massive success in the second tier of English football.
“They have some exciting potential in the youth academy and if Jack Grealish is ever to pull his finger out and prove he wants to play, now is the time to do it,” the former Liverpool and Tottenham midfielder wrote in The Daily Mail.
“He could tear the Championship apart if he shows the right attitude and Villa build a team around him.”
Grealish is a very talented young player, but his progress this season has been stunted. The 20-year-old has scored one goal and created 11 chances in 14 Premier League appearances for the Villans so far this campaign.
The youngster has a pass accuracy of 86% and a shot accuracy of 50%, and has won one header, 22 dribbles and five tackles.
Grealish needs to prove himself in pre-season training and then make the most of the chances in the opening weeks of the 2016-17 Championship campaign.