Mikel Arteta said he was worried by the 'unacceptable' defensive performance from his Arsenal side in their 3-3 draw with West Ham on Sunday.
Jesse Lingard put West Ham ahead with a wonderful first goal before setting up the second for Jarrod Bowen, and Tomas Soucek then made it three.
Own goals from Soucek and Craig Dawson, plus a strike from Alexandre Lacazette ensued the points were shared at full time.
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However Arteta focused on the errors from his side before their comeback, telling Sky Sports: "I'm very disappointed because I cannot accept my team to play the way we did in periods in the first half. I expect we play at the level we did afterwards.
"The first goal, it can happen. It is a really good combination [by West Ham]. That is fine. The way we concede the second and third is unacceptable. Afterwards the attitude and togetherness we showed - it is really difficult to do what we have done. We got really close to winning and I think we deserved to win it but the first part really worried me."
Moving onto the second goal, he said the set piece was: "Unacceptable. We talk about that all the time. I don't know if it's a hangover from Europe, tired, focus, it was more than one player that switched off. We have to right that quick."
There was one bright spot as far as the Spaniard was concerned, with Calum Chambers impressive as he continued his return to action following a lengthy absence due to injury.
"He was really good, he has been training really well," Arteta said.
"He gives us something else, some height in the back line and he was busy in the final third as well. A really good performance."
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