Former Arsenal manager George Graham says Arsene Wenger needs to bring in a different style of player if the Gunners are to win trophies again.
Speaking on Radio 5 live's Sportsweek, Graham said Arsenal will struggle to finish in the top four this season.
"They look a bit vulnerable. Everyone knew Fabregas was going," he said.
"I can't believe they haven't got replacements in already. They need experienced players in to help all the outstanding youngsters they have got."
Graham praised Wenger for creating three title winning sides, but said the current squad was markedly different from the one that went through the 2003-04 season unbeaten in all 38 Premier League matches.
"When they had the great 'Invincibles', that team had everything: technique, power, physical presence, great mental players - everything you would want in a football team," explained Graham.
"They've moved away from that, into a copy of the Barcelona team - small players, very mobile, very technical.
"But in English football you need more than that, you need power, and physical players.
"The money has come in but it looks like they've left it too late."
Wenger has transfer cash to spend after the sale of captain Cesc Fabregas to Barcelona, along with Gael Clichy to Manchester City and Emmanuel Eboue to Galatasaray.
Samir Nasri's proposed move to Manchester City is still alive, despite reports of a hold-up in negotiations between the two clubs.
Graham continued, "I think they need another three [players] in the side at the present time.
"It's just a matter of doing what Manchester United do - go out and buy a couple of players at £30m.
"Please get the the cheque book out Arsene. I think they need another centre-half, I think they still need a strong, outstanding, experienced midfielder and I still think they need an out-and-out striker like a [Thierry] Henry.
"They have big signs at the club saying 'Arsene knows'. Well I hope he does.
"But I think Arsene, if he sits down and is honest with himself, he'll put it all back together again. But he needs to do some hard thinking."
Arsenal travel to Udinese on Wednesday defending a 1-0 first-leg lead in their Champions League play-off. They have started the Premier League season with a draw at Newcastle and Saturday's home defeat by Liverpool.
They have yet to score in the league and had Emmanuel Frimpong sent off against Liverpool to add to Gervinho's red card against Newcastle.
Midfielder Alex Song has been banned for three matches after accepting a charge of violent conduct in the match at St James' Park.
Graham won two league championships with Arsenal during his nine-year tenure as manager at Highbury, as well as the FA Cup, two League Cups and the Uefa Cup-Winners' Cup.