The 26-year-old joined Man City from Aston Villa in a deal worth £100 million last summer.
But he failed to make a huge impression, as he opened up on his debut season at the Etihad in a candid and honest interview following the final game of the 2021/22 Premier League season.
Souness has slammed Grealish's first season at Man City, claiming he 'doesn't see any improvement' from the England international since moving to Pep Guardiola's team.
Speaking on a panel for Sky Bet, he said: "He’s not a quick learner. All the top players are quick learners. Jack’s had a year and for me he’s not improved."
Responding to Micah Richards defending the superstar forward, Souness replied: "I have not mentioned his transfer fee.
"City have got some world-class players. I’m looking at what he gives in the 90 minutes.
"I don’t see any improvement at all in him. Top players are quick learners, Micah."
Roy Keane pulled no punches, too, as he claimed the 'penny has to drop' with the player.
"We’ll try and give Jack the benefit of the doubt," said the Manchester United legend.
"He’s about 26-27 now, you’re thinking he should have gone to City and maybe adapted a bit quicker, but sometimes it can be difficult.
"He’s gone in and he’s not really had the run of games, he had one or two injuries earlier in the season.
"He would have been disappointed, even at the last game being left out against his old club Aston Villa, but they got over the line and you’d fully expect Jack to have adapted more to the demands of Man City and of Pep.
"I think Pep would have certainly been intense with him and maybe Jack wasn’t quite used to that.
"We’ve seen him being left out of big games for City, and Gareth (Southgate) has done the same with England, so the penny has to drop for Jack.
"You want to be a real top player; you’ve got to maybe step up to the plate a bit more and the manager has got to have a bit more trust in him."
Grealish made 36 appearances in all competitions last season, scoring just six goals.
Having had a season under Guardiola's tutelage, he'll be hoping to kick on next season and make a real impact for the defending English champions.
Featured Image Credit: Alamy/Sky Bet
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