The former City keeper believes the Scot's decision presents an opportunity for Manchester United's Premier League rivals.
"For more than 20 years Sir Alex Ferguson ruled the roost," he told the Manchester Evening News. "Not just by having the best team but by having the best manager. His managerial style was unique and obviously very, very effective.
"They'll lose that with David Moyes. But also the managers that suffered in Sir Alex's wake - the likes of Arsene Wenger - have an opportunity to make more of a mark. There's potential there for the most exciting Premier League season."