Since Manchester City secured their historic treble, the players and Grealish have been painting Istanbul, Ibiza and Manchester blue with their non-stop partying.
Grealish has of course lived up to his party animal label over the past few days, the England forward seen with an assortment of booze in his hands throughout the past 72 hours - he admitted during City's bus parade on Monday evening that he's not slept since Saturday's Champions League final.
But it finally appears to have all caught up with him as Bullard revealed on Drive.
"I texted him earlier telling him I'm coming on talkSPORT etc, saying, 'I love ya, good luck, how's your three trophies?'" Bullard said.
"He texted back, saying, 'Wow, I'm in a world of pain' What a legend!"
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Grealish's post-Champions League antics, as well as his celebrations after City won the Premier League last season, have gone down a hit with many fans.
Some naysayers will believe he should have been more responsible, however, Bullard insists that someone of Grealish's character is crucial for any successful team.
"I've been a massive Jack fan since before all of this, I've seen it coming a long way off," Bullard added.
"To have a character like that in the changing room alone and around all the players... I can relate to it a bit but I'm not putting myself in the same league as Grealish as a footballer, but being that character is an addiction.
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"He'll be going in and playing that laddy character. He's had it all his life and I think that's a massive pull. The City team doesn't have a great English contingency. To have Jack, he's at the heart of everything and every celebration which is important.
"I love the boy. I think he's unbelievable for English football.
"I hope people don't put him on a pedestal too much and then chop the legs off of him, let Jack be Jack. Let him celebrate when he wants to celebrate.
"Do what you want, Jack. You've got to realise how young they are, these are young footballers who have got the world at their feet.
"Be careful, look after him. We've done it before with others before him. And he's celebrating like a young man should do, he's achieved great things."