"I feel they lost their motivation. I even fear that some have lost faith in Arsene," Petit, part of Wenger's vintage 1997/98 double-winning side, told France Football magazine.
"Ninety five percent of the players can do better. But I feel there is a communication problem. Each player seems to be in his own world. These players are fragile. They can crumble."
Arsenal face another trophy-less season after losing the first leg of their Champions League last 16 tie away to Milan 4-0 and going out of the FA Cup to Sunderland.
They are fourth in the Premier League, 10 points behind third-placed Tottenham who they face at home on Sunday.
Petit, whose midfield partnership with fellow Frenchman Patrick Vieira was key to much of Arsenal's success under Wenger, said some of the players needed to show they cared.
"I went twice in the dressing rooms after the Villa and Leeds games. Titi [Thierry Henry] was still there 40 minutes after the final whistle... but half of the others were gone already." he said.
"Football is not a popularity contest on Twitter or Facebook. Pull your fingers out, chaps!" added Petit, who described some of the current squad as acting like "peacocks in a farmyard."
