However, the 20-year-old is poised to rejoin the senior squad after playing for the reserves against Derby County.
"Jack Grealish will play for the reserve team on Monday and will probably rejoin the group after that," Garde was quoted as saying by the club website (www.avfc.co.uk).
The manager, whose side prop up the Premier League table and are six points adrift of second-from-bottom Sunderland, hailed his team's unity after they secured a 1-1 draw at Southampton on Saturday.
"I saw solidarity between players and the desire to fight all together and not concede goals," he said. "We didn't have the same attitude at Everton or even in our last home game against Watford (a 3-2 defeat).
"Solidarity for me is the key when you are fighting not to be relegated. If we show this kind of performance again in terms of spirit in the team, we will get more points."
(Reporting by Simon Jennings in Bengaluru; Editing by John O'Brien)
