The Gunners won 6-1 at Emirates stadium.
"They (Arsenal) were outstanding, the movement they have got will teach us a lesson," he said.
"We ran out of legs and that is something we have got to work on.
"We have got to make sure that we can sustain a performance for 90 minutes because we couldn't.
"That is where the goals came from, we tired terribly and we need to really work at that and address that."