Martin O'Neill has refused to explain why he left Aston Villa just days before the start of the season in 2010 ahead of his first trip back to Villa Park with current side Sunderland.
O'Neill was at Villa for four seasons and achieved three consecutive sixth-placed finishes before his dramatic departure just five days before the start of the Premier League campaign.
Eight home draws in his final season prevented Villa from finishing in the top four and he left amid rumours of rows with owner Randy Lerner over transfer funds.
The Sunderland boss refused to comment on his exit, hinting only that things turned 'sour' behind the scenes.
"I had the privilege of managing one of the great clubs of English football with a great tradition behind it," he said.
"I was there for four years and the fourth year was a bit sour unfortunately.
"Ironically, it was the best year having finished six points off the Champions League.
"There may be clearing up at some stage on the reasons for my departure but having been gone for two years, I'm not sure any explanations on the eve of this game is the right thing."