London, Nov 5 - Arsenal let a golden opportunity slip through their fingers and must become more ruthless, captain Mikel Arteta said after the Gunners wasted the chance to reach the Champions League last 16 with two games to spare on Tuesday.
The Londoners were 3-0 up and cruising against Anderlecht only to concede three times in 29 minutes to draw 3-3.
"When you are 3-0 up, in a big game like this, an important game like this, because we could have been through the group stage, we missed a tremendous opportunity," Arteta, who opened the scoring from the penalty spot but later went off with a hamstring injury, told Arsenal's website (www.arsenal.com).
"You can't afford to make mistakes like this and give any hope to any team in the Champions League because they have the quality to hurt you and that's what happened.
"We can't give those chances away because you don't know what's going to happen in the next (game). When you have opportunities like this, being 3-0 up, it doesn't get any better than that, so we are very frustrated, very disappointed.
"We need to analyse what we've done because it's not good enough. What happened and it can't happen again."
Arsenal are still well-placed in Group D with seven points but manager Arsene Wenger believes it will be almost impossible to finish as group leaders as Borussia Dortmund, who they host next, have a maximum 12 points.
They will need only a point against the Bundesliga side to reach the last 16 for the 15th season running, but defeat could set up a nerve-jangling night in their final match in Turkey against Galatasaray.
Of more immediate concern for Arteta is that Arsenal bounce back with a victory over Swansea City in the Premier League.
"That's the best thing in football, we have another game in four or five days against Swansea away, and it needs to be different," he said.
He is unlikely to feature, however, according to Wenger.
"He has done a hamstring. I don't know what is wrong or how long he will be out for," the Frenchman said.