Arsene Wenger believes his side must lay to rest their defensive "ghosts" before they can move forwards in 2015.
The Gunners begin the defence of their FA Cup crown at home to Hull on Sunday having started the new year with a disappointing 2-0 defeat at Southampton, which left them in sixth and three points off the Champions League places.
Having produced such a solid rearguard display when winning at West Ham on December 28, Arsenal were again architects of their own downfall at St Mary's with blunders from goalkeeper Wojciech Szczesny compounded by poor judgements from centre-backs Laurent Koscielny and Per Mertesacker which proved so costly.
Wenger is expected to rotate his squad for the FA Cup tie, with Colombia goalkeeper David Ospina already set to stand in for Szczesny, the 24-year-old Poland stopper again seeing his position as number one come under scrutiny.
Arsenal host Stoke on January 11, and then travel to Manchester City - by which time Wenger knows his defence must pull themselves together.
"I cannot fault the attitude of the team, but we were again haunted by the ghost of what we have seen since the start of the season," Wenger said on Arsenal Player.
"This is not the first time it has happened. We did not defend well enough in the final third, and we paid a heavy price. It is a self-inflicted defeat."
Mertesacker - who failed to clear a looping shot from Sadio Mane as it bounced over the line after Szczesny had rushed from his goal - accepts there will be some soul searching as the Gunners look to rediscover the form which had seen them head to Southampton on the back of just one defeat out of nine games in all competitions.
"The last two matches we were in good spirits and those games were close together (over Christmas) and we fought really hard for the two wins, but at Southampton, it was slightly different, we didn't show up with a good performance," said the 6ft 7ins German centre-half.
"We have to come back to our main strength and we have to remind ourselves every day that we need to have a big performance."
Striker Danny Welbeck (thigh) missed the Southampton game because of a thigh problem, and Olivier Giroud serves the last part of his three-match suspension for Sunday's cup tie.
Germany international Lukas Podolski did not feature because of a tight groin, according to Wenger, with Inter Milan set to step up their interest when the transfer window officially opens again.
Wenger said: "I will make a few changes (against Hull), that is for sure."
Teenage forward Chuba Akpom came off the bench against Southampton, and the 19-year-old would relish another taste of first-team action this weekend.
"I am hungry for it now. I want to show the boss what I am made of and I think that I am ready," he said.
"I think I can have a good impact on the team, hopefully I get a chance."
