David Moyes admitted West Ham United weren't able to deal with Arsenal's intensity on Wednesday.
The Hammers went down 2-0 at the Emirates Stadium.
Moyes said: "I did not think a lot of our performance generally.
"Arsenal played well with good intensity and we were not able to deal with it.
"We showed resilience to stick in the game but made a couple of really poor bits of play that led to the goals.
"We gave the ball away for the second goal when we were in the ascendency."