"We were disappointed with the performance and the result," said Pearson.
"Once we got our noses in front we should have won even though we were not playing particularly well.
"This was the most disappointing aspect of the game but Bryan Robson has told the players in no uncertain terms that level of performance is not acceptable.
"We are not very happy. But we were not beaten and we move on.
"I thought the two centre-backs played quite well in a game which some people thought we might have been beaten.
"It was up to us to put our authority on the game but I don't think we did that."