The Dutchman is out for six weeks with an ankle injury.
"We had some deficiencies which we paid for and we have to make sure that is not repeated," said the Arsenal manager. "We did not produce enough in the final third, which had been our strength until now.
"We did not have the right fluency in our game, nor enough penetrative runs to force the issue in the final part of the pitch.
"That is why we were not dangerous, rather than down to any individual.
"I do not deny at all the super-class of Van Persie, I just feel we still have enough in the locker to score goals even when Robin is not there."