Kelly was renowned for his fast-paced offense while in charge of college side Oregon and that was no different for the Eagles as they racked up 53 plays in the first half alone at FedEx Field.
"I felt like it was slow. I'm not joking," Kelly told reporters. "We need to do a better job. We left the ball on the ground too much.
"We didn't get the ball to the officials. We could have sped things up from a process in between plays. That's something we need to work on."
Philadelphia face the San Diego Chargers in week two.