A rampant Liverpool punished a lacklustre Arsenal side with four goals in under 20 minutes.
A pair of braces from Martin Skrtel and Raheem Sterling, and a goal from Daniel Sturridge gave Arsenal a nightmare start to a terrifying couple of weeks as they dominated from start to finish.
Wenger believes the defeat 'raises some questions' as Arsenal surrendered their top spot in the Premier League.
"Only our fans were good for 90 minutes. All the rest, we were poor," Wenger is quoted as saying on ESPN.com
"It was a very poor day. We were poor defensively, offensively.
"Liverpool played very well, so congratulations to them. But it was a poor performance on a day when we couldn't afford it.
"Of course it raises some questions today because we were caught many times and were naive. Defensively we need to be more stable.
"Today we were too open. From the front to the back we were not at the level we are used to."
A penalty from Mikel Arteta was never going to be anything more than a consolation - cue the muted celebrations from Arsenal fans who, ironically, were louder throughout the game than when they scored.
The defeat - and more so the manner of the defeat - will once again raise questions about Arsenal's capability to challenge for major honours.
The Gunners will now look to bounce back on Wednesday night when they face another difficult challenge in the form of Manchester United.