Roy Keane called on Jack Grealish to "grow up" before Manchester City's FA Cup win over Peterborough on Tuesday night.
The former Aston Villa man, who is now the most expensive British player in history, headed to the Etihad in the summer.
Grealish has shown quality in glimpses but has been unable to nail down a regular spot in a team full of stars.
Competition is fierce whilst Pep Guardiola places huge demands on his players.
Grealish played in the 2-0 win at London Road, but before kick-off Keane suggested that the player's off field antics were resulting in a lack of trust from his managers.
"I think it’s crunch time for Man City over the next few months," Keane said on ITV. "This is where you will really test as a player, crunch games.
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"Jack’s had a few injury problems, [and has] probably been criticised a little bit for his off-field stuff but I think what Jack has to do is grow up and get the trust of Pep.
"He probably hasn’t got that yet, same with England, I don’t think Gareth [Southgate] trusts him that much yet.
"[It's a] good opportunity for him [against Peterborough]. Whatever Jack’s doing off the field, it does take its toll when you’re an attacking player, it’s another opportunity for Jack. I do think it’s about time he grew up."
Grealish has made 26 appearances this term, scoring on four occasions, including one against Peterborough.
His efforts with Villa over the years have seen him earn international recognition with England.
The 26-year-old has had to be patient however with Gareth Southgate tending to prefer other options.
Grealish was on the pitch when the Three Lions fell short in the Euro 2020 final with Keane criticising the City star for not stepping up in the penalty shootout.
"If you're Sterling or Grealish, you cannot sit there and let a young kid walk up ahead of you," he told ITV Sport.
"You can't sit there, see a young kid at 19 who is shy walking up in front of me, and I've played a lot more games and have a lot more experience?"
Grealish responded on social media however, insisting he put his hand up to take one.
He claimed: "I said I wanted to take one!!!! The gaffer has made so many right decisions through this tournament and he did tonight! But I won’t have people say that I didn’t want to take a peno when I said I will…"
