The French World Cup winner, who secured a double with the London club in 1998, criticised the current transfer policy and insists experience is needed at the Emirates
The Gunners were eliminated from the FA Cup on Saturday, losing 2-0 away to Sunderland, whilst they look to be out of the Champions League having lost 4-0 in the first leg of their tie with AC Milan.
They are also 17 points below Premier League leaders Manchester City in fourth place and look set to finish without a trophy for the seventh successive season - their last win coming in the 2005 FA Cup.
However, although former Gunner Petit believes Wenger is currently at a low ebb, he insists that the players should take some responsibility.
He told BBC: "This is the worst moment of Arsene's career with Arsenal.”
“The players have to look in the mirror, be honest and ask questions of themselves.
“They are playing like they don't know what's going on, they don't know what to do on the pitch. Mentally, they are very weak.”
Arsenal were defeated at the last minute in the 2011 League Cup by Birmingham City, and Petit recalled that loss as the moment when their problems intensified.
He added: "Birmingham was the crucial point. From then on, the players started to lose confidence in the policy at Arsenal.
"Arsene built success based on experienced players and big characters. All of a sudden he decided to completely change it, put confidence in young players.
"For five years they were close to winning something but they didn't and that's why they have to change the policy.
"They have to bring in more experience and big characters. They need leaders. But you cannot sign big players if you are not in the Champions League."
The Frenchman also spoke of the destabilising effect of the summer sales of Cesc Fabregas and Samir Nasri to Barcelona and Manchester City respectively.
He continued: "How they managed that was terrible. Nothing was controlled. Everything was done so quickly without thinking.
"Every year they're selling their best players. Arsenal are not a football academy - they're one of the biggest clubs in Europe and need to get back to that level.
"They have to spend money to get the big names, and they must also ask some players to leave."
How do you stay up to date with football when on the move? With http://m.goal.com – your best source for mobile coverage of the beautiful game.