Mikel Arteta admitted his side were 'nowhere near the level' as Arsenal suffered a 2-1 defeat to Fulham to miss the chance to end the year at the top of the Premier League.
Arsenal had taken the lead at Craven Cottage through Bukayo Saka, but Raul Jimenez and Bobby Decordova-Reid turned the game around for the hosts.
The Gunners have ended the year with back-to-back defeats following their 2-0 home defeat to West Ham on Thursday.
Arteta claimed his side were 'not good enough' against Fulham and branded their performance as their 'worst of the season'.
'We weren't good enough, it's that simple. A few days ago we lost a game that we deserved to win, but today we were nowhere near that level,” Arteta said.
Mikel Arteta labeled Arsenal's performance against Fulham as their worst of the season
Your browser does not support iframes.
'You have to play 100 minutes in this competition, it's a really sad day because we didn't deserve to win the match.
'To definitely try to change the dynamics of the game, to have more threat, but we couldn't get going because we were giving away every game. It was difficult to create momentum.
'The way we conceded the goals today is football and also an honor for Fulham.
'We played great against Liverpool and West Ham, but we didn't win.
“Today you need to isolate as it was the worst of the season.”
The Arsenal boss was asked what his side needed in the January transfer window to achieve their goals for this season.
Arteta's response reduced the chances of signings as he claimed the club would continue to play 'with the same players'.
The loss to Fulham leaves Arsenal two points behind Premier League leaders Liverpool and Aston Villa, and level with reigning champions Man City.
Liverpool and Man City have a game in hand against the Gunners, with the former having the chance to finish clear at the top when they host Newcastle on New Year's Day.
Arsenal, who have dropped to fourth place, are now just one point ahead of arch-rivals Tottenham.