Mertesacker: 'We need to be more focused'
Defender Per Mertesacker warned Arsenal must develop a focused mental attitude if they are to avoid being left behind in the Champions League.
The Gunners saw their European aspirations ended at the last-16 stage once again despite Tuesday night's 2-0 victory in Monaco, which saw them go out on away goals.
Despite all of their success in qualifying for the group stages, it is now five seasons in a row that Arsenal have failed to reach the quarter-finals of the Champions League.
Manager Arsene Wenger lamented the costly 3-1 home defeat in the first leg last month, when a breakaway stoppage time goal proved fatal just moments after Alex Oxlade-Chamberlain had scored what should have been a lifeline.
Centre-back Mertesacker, who captained the side at the Stade Louis II Stadium, accepts Arsenal cannot afford such lapses in concentration if they are to compete with Europe's elite clubs on a consistent basis.
"In the first game, we didn't have that mental level you need to compete at the highest level. That was missing but you could see on Tuesday night in Monaco how good we are as a team and how well organised we can be," the German World Cup winner said.
"We need to consider that every day in training and in games, that is why we are so far away from winning the Champions League.
"It is the last 16 and Monaco were underestimated by a lot of people, but they deserved it by playing well in the first leg.
"We had one bad game and that is enough to get knocked out.
"In the first leg, we conceded that late goal which was overall the killer, so it is really disappointing for us."
Arsenal almost upset the odds in the principality tax haven, famed for its casinos and yacht-lined waterfront.
Despite having come up just short in their historic bid to qualify from such a first-leg deficit, the Gunners remain in good overall form.
The victory in Monaco, who had not conceded a goal at all during the Champions League group stages, was a 15th win from the last 18 matches in all competitions.
Aaron Ramsey, who scored a second goal on 79 minutes to pile on the pressure after Olivier Giroud's first-half opener, is confident for the challenges ahead.
"We could take some positives from the Monaco performance and hopefully we can get back on track against Newcastle this weekend and we can keep that running run we are on," the Wales midfielder said.