Back in the summer of 2016, the verbal jabs and social media snipes were flying in Grealish's direction, as his decision to turn his back on a career with the Republic of Ireland and play for the country of his birth appeared to be backfiring.
Ireland were playing at Euro 2016, while Grealish appeared to a long way from the England call-up he would have been hoping for after he opted to turn his back on the chance to play at senior international level with Ireland.
Jack appeared to be developing a reputation as a bad boy who was in danger of going off the rails, as he struggled to make his mark at Aston Villa and hitting the headlines for the wrong reasons as his off-field travails.
Yet after after making an impressive contribution to England's 1-0 win that secured their place as Group D winners in Euro 2020 on Tuesday night, Grealish is now every inch the football A-lister he was expected to be when he was making his decision over his Irish allegiances.
Premier League champions Manchester City are expected to make a move to sign him this summer, with a former team-mate telling sundayworld.com that his rebranding has been a triumph for a player who was always destined for greatness.
Micah Richards became a big brother character for Grealish as he grew up in front of the world's media over recent years and he has told us that the boy who made mistakes is now a man ready to shine on the biggest of sporting stages.
"There were days in training when I looked at Jack and questioned how he was doing the things he was doing," Richards told the Sunday World at a Sky Sports event.
"Jack and I became close friends during my time at Villa Park and it has been brilliant to watch him fulfil his potential.
"I'm a few years older than him and whenever he had a dilemma he always used to ask me questions about what I thought he should do.
"Some of them were about possible transfers. He had offers and opportunities to leave Villa, but I would just tell him "it is your career - make sure it is you who decides what you do".
"He had some off-field issues to deal with too, where I was able to give him advice on his lifestyle because I had made the same mistakes myself.
"When you are young, famous and earning quite a lot of money, things can get on top of you and you can end up mixing with the wrong people.
"It's hard to keep your feet on the ground, and knuckle down and focus on football in the way you should be doing to push on as a player.
"Now he has lived his dream by playing for Villa for a few years and we wait to see what happens this summer."
Richards went on to suggest Grealish should be "one of the first names" on Gareth Southgate's team-sheet as England attempt to win Euro 2020, as he admits the time may soon be coming for him to leave his beloved Villa.
"One thing for certain now is Jack Grealish has proved he can play for any club in the Premier League and I mean any club," added Richards.
"You have to remember that Jack grew up a fan and he would die for that club. This means a lot to him and his family to play for Villa.
"There may come a moment when he feels he needs to move on, but he won't make that decision lightly. Jack loves Villa and it is up to the club to convince him they can give him everything he wants from his career."
Grealish heads into today's game against Leicester with the glowing endorsement of Foxes boss Brendan Rodgers ringing in his ears, with the Irishman suggesting Villa's star man is now a mature performer.
"His personality on the field is absolutely fantastic. He's got a real in-built brain for football," says Rodgers.
"When he carries the ball, his awareness of his space really shows me the talent he is.
"He understands where space is, he gets tackled a lot, he stays on the ball a bit longer than other people and draws fouls but also draws people out of position.
"His weight of pass is exceptional, his composure on the ball is that of a player who has something special. That's why Jack Grealish is now the player we all thought he would be. And he could get even better."
After a period of uncertainty over this issue, Ireland's loss is very much England's gain in the end.