The Frenchman was disappointed as Hull City striker Daniel Cousin was able to head home the winner for the Tigers on Saturday and has questioned the defending of William Gallas and Kolo Toure.
Wenger has no doubt about their ability but is concerned with the lack of height and that could open the door for youngster Johan Djourou.
"I believe that we have more a size problem than quality in our defending problem," Wenger said. "Our centre backs are not very tall. I don't know what we can do. It's not only centre backs who defend. As a team we are a bit short.
"I do not necessarily think it's inexperience. We gave them too much room on the first goal and we didn't clear the ball on the second one, and that's basically it.
"I don't know how many games we can afford to lose in the league. What is important now is to recover and prepare for the next one. Can we afford to lose not one more? I don't know."