Speaking in the Sunday Mirror, O'Leary said: "I was gutted when they sacked me because I thought I was doing a good job.
"I still love the club and want it to do well. But what really concerns me is that it seems no one will take the manager's job.
"I suppose somebody, thinking they've nothing to lose, might have a crack. But that's hardly the best basis on which to take a job.
"I feel so sorry for the fans. They had a wonderful five years when anything seemed possible.
"The club was in Europe every season, reached the semi-final of the Champions League and had some marvellous players, especially youngsters. The future was bright but now they may not even have a future."