Niall Quinn's "magic-carpet ride" at Sunderland finally came to an end on Monday when the club's former chairman stepped down from his post as international development director.

The 45-year-old former Sunderland, Manchester City, Arsenal and Republic of Ireland striker said he intends to concentrate on spending time with his family near Dublin as well as developing new business interests away from football.

Quinn's powers of persuasion helped create the Drumaville consortium which took control of Sunderland in 2006. Working alongside that group of Irish businessmen he served as chairman before accepting an international development role in October last year.

By then, Drumaville had been bought out by Ellis Short, with Quinn having persuaded the billionaire American financier to buy Sunderland. Once the Irishman had relocated to international development Short completed a mini overhaul of the board which, most notably, saw the 31-year-old lawyer Margaret Byrne become the club's chief executive, by succeeding Quinn as chairman.

Although Quinn spent most of his final months at the club securing new international partnerships in Africa and east Asia, perhaps his most important job was in helping Short recruit Martin O'Neill as Steve Bruce's managerial replacement in December last year.

"Niall has been a truly iconic figure at Sunderland, both as a player and in his time leading the club from the top," said O'Neill. "His vision and drive, alongside that of Ellis, played a significant part in me coming here.

"Like everyone, I couldn't be more disappointed that he has decided to step down, but of course I respect and understand his decision. He has been the heartbeat of the football club for so long and his legacy is immeasurable. To me, he is 'Mr Sunderland' – and always will be."

Quinn, who shortly before appointing Roy Keane as Sunderland manager in 2006 promised fans a "magic-carpet ride", believes he is leaving the club in rude health.

"Sunderland is in an incredibly fortunate position to have a hugely talented team of people leading the football club right now," he said. "Everything is in place for Sunderland to really make a statement, which was always my aim.

"From a football perspective, securing the services of Martin O'Neill has been an absolute highlight. In Martin we have a man that understands the region, the club and the unique place it holds in the lives of its supporters, and I am confident that he will harness the immense passion that exists here and take us to new heights.

"I am now looking forward to spending more time with my family and exploring business interests away from football. One thing is for sure though, I'll still have that knot in my stomach before kick-off and the feeling of pure elation at the final whistle if the result has gone our way – that will never leave me."

While David Miliband, Sunderland's vice-chairman, reflected that Quinn would make "a great politician", Short paid tribute to the man who drew him to the Stadium of Light.

"Niall Quinn is and always will be a Sunderland legend. His vision brought me into the club and that vision still inspires what we do," he said. "He has been a trusted friend and adviser to me throughout our time together at Sunderland, and while I'm sad about his departure, I respect his view that his 'work is done'. My job is to carry on that work."