Aberdeen Chairman Stewart Milne has said he always felt it was 'at least 50/50' that Derek McInnes would choose to stay at Pittodrie.
The 45-year-old had been interested in making the switch to Wearside but pulled out of the deal just as the Black Cats began to believe they were closing in on an appointment.
That turn of events has been seen as a major boon for the Dons, who have secured new major investment from Dave Cormack and are hoping to begin the process of building their own training ground and a new stadium.
McInnes had been expected to leave the Scottish Premier League but Milne says he always felt he had a chance of convincing him to stay.
He said: "I've built up a very close relationship with Derek over the last three or four years, we've been in constant dialogue over the last four or five days.
"I always felt it was at least 50/50 and I was obviously delighted that he phoned me yesterday morning and said that he was absolutely committed to the club. If he'd made a decision the other way it would have been a massive wrench for him to walk away. He has come to see Aberdeen football club as his."
Milne says losing McInnes would have been a 'massive blow' and added that Scottish football will be stronger for his decision.
He told STV: "I think it's a very positive thing, not just for Aberdeen - I think it's a fantastic thing for us - but I think it sends out a very positive message to the rest of Scottish football.
"Having guys like Brendan Rodgers and Derek in Scottish football is a massive thing.
"If we can, along with Celtic and Rangers, start making some inroads back into Europe again then I think we're starting to rebuild the profile of Scottish football.
"It would have been a massive blow for the club," he added.
"It's not just what he's done on the park over the last four years, he's helped us rebuild the whole operation around the football side.
"He's brought a great deal, in almost every aspect of the club, over the last four years that the whole atmosphere throughout the club we've been able to lift.
"Derek has played a big, big part in that."
Sunderland's Chief Executive Martin Bain has said that a decision was reached jointly not to continue negotiations and that the recruitment process will continue.
In a statement, Bain said: “We have been in discussions with a number of potential manager candidates over recent weeks.
"In the last few days we have been negotiating with Aberdeen Football Club in order to allow us to speak with Derek McInnes.
“Having held initial discussions, both ourselves and Derek have decided not to progress with further talks and we will continue with our recruitment process”.