Allardyce signed Barton for Newcastle in June 2007.
And he said: "I was watching his performances from afar and admiring them over a period of time and how he had overcome his injuries to show the potential I knew he had.
"To have him slip up is a great shame, considering how far he had come to be knocked back. He is a great footballer but it's a mad moment.
"I hope it's a one-off, he hadn't done something like this for a long time."