Per Mertesacker has lamented Arsenal's lack of concentration in the first half of matches this season which he claims has prevented them from cementing a top four position.
Mertesacker, 28, admits the Gunners wasted an opportunity to move closer to securing Champions League football for next season after a 2-1 loss to Tottenham in the North London derby on Sunday.
Goals for Gareth Bale and Aaron Lennon within the space of three minutes left Arsenal reeling as they headed into the break at White Hart Lane, meaning Arsene Wenger's side have now conceded four first-half goals in their last three matches.
"We are disappointed because we looked good for the first 35 minutes," Mertesacker said. "We'd been solid at the back, high up, but then we couldn't manage both situations where they scored.
"I thought we were good in the beginning but we need to maintain that level and that's what we are lacking all the time, that consistency over 90 minutes - or at least to keep a clean sheet for the first 45 minutes.
"That was our first target. We switched off, we expected there to be a foul called on someone but you can't switch off at any time in the game."
Arsenal have a much-needed gap ahead of their Champions League round of 16 second-leg tie against Bayern Munich and Mertesacker believes the rest gives him greater hope of overturning the 3-1 deficit.
"We need this breather now. We have 10 days until our next game so we can think about our situation," he said. "Of course there is potential but we need to show that on the pitch.
"That's what we need in the next few weeks, to go to Munich, to show responsibility for the Champions League. We have to take the chance there and afterwards we have to take care about the league and try to go for all points."