Garde has been critical of Grealish’s work-rate since taking charge, and he has apparently already put him back down to training with the Under-21 side.
The youngster was alleged by the Daily Mail to have been at a party after Villa’s defeat to Everton on Saturday evening.
Grealish is regarded as one of Villa’s most exciting prospects in recent times, but he has not been at his best this campaign.
The attacking midfielder’s desire has been called into question, and there are now doubts over whether he will play for Villa at the weekend, when they take on Watford.
Garde left Grealish out of his first starting line-up against Manchester City, but the Frenchman did recall him for their latest outing against Everton.
Unfortunately for the 20-year-old, he failed to make an impact – and Villa were beaten 4-0 by Everton, leaving them sitting at the bottom of the Premier League table.