They trailed by three goals at half-time, and never looked like getting back into the match. It finished 4-0 to the home side in their first appearance at Cardiff City Stadium.
"We had an early chance and presented Cardiff with problems until they scored," said Adkins.
"I'm told that the second goal could have been disallowed for offside but then the third killed us.
"We did all right in the second half and kept the ball far better but it was disappointing to give away that late penalty.
"Today we were given a hiding but the players must respond in the right way. We know we need to defend much better but it would have been a big shock if we had taken anything from this game which gave our players a real welcome to the Championship."
Dave Jones, the Cardiff manager, was delighted to finish the opening day of the season on top of the table.
"We rode our luck in the opening quarter but after that we played some good football and the team as a whole played well," he said.
"It was a case of making sure we kept them out in the second half but with all the debutants playing well to start the season with a 4-0 win in a new stadium was outstanding for our supporters."