Ellis Short has insisted that he had no choice but to sack O'Neill and the appointment of Di Canio will prove to be the right decision.
"The simple answer as to why we changed managers was because our results and performances on the pitch hadn't been good for over a year," Short told Sky Sports News.
"The decision to change manager was made with only one aim: to give us the best possibility of staying in the Premier League.
"I am excited that we were able to bring in Paolo. I like his willingness to do whatever he and his team have to in order to give us a successful end to the season."
Short has been chairman of the Mackems since May 2009.