Abou Diaby maintains Arsenal can only learn from their mistakes to be stronger in Europe this season.
The Gunners threw away what would have been a third straight European victory, and all but securing safe passage into the knockout stages, when they allowed AZ Alkmaar to snatch a stoppage-time equaliser in Holland on Tuesday night.
"We will take a good lesson from this," said the midfielder.
"We need to stay focused until the last minute, so we need to work on that.
"We can still improve in these situations, to be focused on the second ball. Now we need to look to the game against West Ham, and be ready for the challenge."
Full-back Gael Clichy has, though, warned his team-mates more lapses in concentration at Upton Park on Sunday will prove costly as Arsenal look to continue their four-match winning streak in the Barclays Premier League.
"West Ham are not doing so well and we are, but we have to be careful," said the French defender.
"We have to be 100% to get the three points.
"I thought defensively as a unit we played well against AZ. We also had some chances to kill the game, but unfortunately we finished 1-1.
"It is a big disappointment, but we must move on."
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