The former Liverpool midfielder took aim at the Villa skipper during his side's 2-0 defeat by Liverpool and questioned why he is the most fouled player in the top flight, although Grealish took to social media to respond.
Souness claimed that he is yet to be convinced by Grealish - a transfer target for Manchester United - and wouldn't want to have the tag as the most fouled player in the league.
He said: "When I was playing I would not want to have been the most fouled player in the Premier League. That means I'm holding onto the ball too long.
"That means I'm not seeing the picture early enough, taking too many touches when I don't need to. There's no doubt about it he has ability, easy on the eye, silky. But I'm yet to be convinced by him."
Alongside an image showing him as second in terms of chances created in the Premier League, the 24-year-old responded: "Can't please everyone."
Villa were beaten 2-0 at Anfield by the newly-crowned champions and manager Dean Smith admits that he is fed up of being a "valiant loser" as they bid to avoid relegation.
The 49-year-old coach said: "To come to Anfield with the way they have played over the last two seasons and to have more shots than them, is something we take a lot of positives from.
"But I don't want to be a valiant loser. Games are running out and we need to put points on the board.
"We have to keep belief in what we are doing. We had a gameplan. We knew if we turned up and tried to out-football the champions and a team that has taken an incredible amount of points over the last two seasons would have been crazy."