The Gunners were out-fought and out-played by the Potters on the day.
"Something has gone - you can see that today," said Wenger.
"It was a disappointing performance. The competitive level for Stoke was higher than ours and overall I think we lost the game because Stoke defended much better than we did, with much more purpose.
"Basically, there is not a lot to say."
"That is the Premier League. If you don't turn up it is the same competitive spirit in every game and you can lose everywhere, especially at Stoke," Wenger said.
"Stoke defend well and make it difficult for you and the most important thing is not to be 1-0 down - and that is what happened with the first free-kick (for Kenwyne Jones' goal).
"In a game like that we turned a lot around but we did not penetrate enough and we were not dangerous enough."