Arsene Wenger warned his young Arsenal side cannot continue to miss "major opportunities" like at West Ham if they are to go on to deliver the Barclays Premier League title.
The Gunners had looked in complete control at Upton Park on Sunday following first-half goals from Robin van Persie and William Gallas. However, Carlton Cole pulled a goal back when rookie Italian keeper Vito Mannone pushed a free-kick into the six-yard box, before substitute Alessandro Diamanti netted a late penalty after Alex Song was adjudged to have tripped the England striker.
And Wenger believes his side missed a chance on a weekend which saw both Manchester United and Tottenham beaten, saying: "It is very frustrating," he said "It is, of course, a major missed opportunity. In our job, you do not have this luxury."
He added: "You need to get points when you deserve to get points and sometimes when you don't deserve to get the points.
"We never got them when we deserved them - and that means we have not made the maximum of what we should have done.
"But we have to keep the positives as we played well and are a strong team.
"We want to learn to finish these games off which is basically the most important lesson of the day.
"We have a great chance [for the title] this year, but you cannot repeat this kind of performance we had and not come out with three points."
While Wenger felt referee Chris Foy was somewhat "generous" with what proved the key decisions, the Arsenal manager called for his youngsters to be more clinical.
"We complicated our game a little bit and had five or six chances in the second half, but we missed the final ball," he said. "That is what we have to learn."
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