Palace fell at the fifth round stage to goals from Daniel Sturridge and Adam Lallana in the second half after entering half-time one up through Fraizer Campbell.
And Pardew, who saw his new side lose for only the second time under his stewardship, says it was one of the worst performances since he took over last month.
Pardew said: “The league is going to be tough, everybody is revving up, Villa have a new manager, so do QPR, we do here, West Brom too.
“It’s going to energise that area, and we need to be focused on that.
“But it was an opportunity today and I’m disappointed how we played in possession. It was one of our worst performances under me.
“We’re better than that on the ball and we need to prove that against Arsenal next weekend.”
Pardew referred to a pivotal moment in the game just before half-time with Palace 1-0 up. Dwight Gayle found himself through on goal with just Simon Mignolet to beat, but the Palace striker was denied by the Belgian.
“That turned out to be a pivotal moment,” said Pardew. “Dwight is very efficient in those areas, I’m surprised he missed.
“We would have been hard to beat if we’d gone in at 2-0 up.”