Thierry Henry has claimed Arsenal are suffering from not replacing his France team-mate Patrick Vieira.
Henry thinks Arsenal are trailing Chelsea because of a lack of depth.
"The most important thing was to make people forget Patrick Vieira left and try to go on a good run and catch Chelsea. We've not done that," he said.
The Gunners' record goalscorer, 28, has less than two years left on his current contract, and has postponed talks on a new deal until the end of the season.
Arsenal have won three out of three Champions League games this season.
But in the Premiership Arsene Wenger's side have suffered three defeats and are languishing in eighth place, 14 points behind Chelsea, albeit with one game in hand.
"In the past I've been asked why we could do it in the Premiership but not in Europe. Now they're asking the other way round," Henry said.
"Without looking for excuses, we've been missing and are still missing key players."
The Frenchman, who this week overhauled Ian Wright's record goals tally with two goals in the Champions League win over Sparta Prague, added: "Some clubs have international players sitting on the bench and in the stands, but we don't have that and it's frustrating."
Henry has been linked with Barcelona and his latest comments will increase fears he is dissatisfied at Arsenal.
The striker has also been at the centre of a dispute between Wenger and the French Football Federation over a charity game.
That match between France and Costa Rica will raise money for air-crash victims and it will be played on Martinique, a Caribbean island where Henry's mother was born.
Wenger will let Henry go, but he is unhappy at the player travelling so far during the Premiership season.
But Henry said: "It would be an immense pleasure to play in Martinique. I can't see myself missing this match. I hope that Arsene will understand that it's very important for me."
Wenger will also have to persuade Robert Pires to sign a new deal.
Pires told L'Equipe: "I agreed with Arsene Wenger to start the season and to have another meeting in January. Then I will see if the club's ambitions please me or not."