Former Leicester City striker Stan Collymore feels that the decision of John Robertson not to join Martin O'Neill at Sunderland was pivotal in the 61-year-old's sacking as the club's manager.
O'Neill and the Black Cats parted company after just 16 months together at the Stadium of Light following the team's 1-0 defeat to Manchester United.
He told talkSPORT: "John Robertson was the conduit between player and manager.
"He hasn't had that sounding board with John Robertson, Robbo decided not to make the trek up north and from what I understand JR almost had enough of the modern-day footballer.
"I think in terms of this season Martin O'Neill just hasn't looked himself. I think that has had a massive impact."
Sunderland are just a point above the relegation zone in 16th place in the Premier League.
