The Italian admitted after his sides' 3-1 Barclays Asia Trophy victory over Tottenham in Hong Kong that the Black Cats had considered coming to a financial arrangement with the former Manchester United man, who has not played a competitive game for the club since January 2012 because of injury.
However, the 33-year-old was desperate to prove he still had something to offer, and demonstrated as much by turning in an impressive individual display and scoring his side's second goal at the Hong Kong Stadium.
Di Canio told the Sunderland Echo: "The club had a conservation with him, but with his strong character, he said 'I feel a footballer, I want to stay here and prove it'.
"Because I'm an intelligent manager, I didn't have any preclusion to anyone doing that.
"He was the perfect professional to have in a squad and what a player. He hasn't stopped for one minute in a training session.
"My pre-season is very tough, but he hasn't had any problems."
Former England international Brown, whose last taste of action came during pre-season 12 months ago, headed Sunderland into the lead 64-minutes into the game after new signing Cabral had cancelled out Gylfi Sigurdsson's opener before the break, and substitute David Moberg Karlsson wrapped up the win at the death.
The Black Cats will play Barclays Premier League rivals Manchester City in Saturday's final after their 1-0 win over South China FC.