Aston Villa boss Paul Lambert ranks Martin O'Neill as the biggest influence on his career along with Champions League-winning coach Ottmar Hitzfeld.
Lambert faces O'Neill when his side play Premier League rivals Sunderland at the Stadium of Light on Saturday.
"Martin and Ottmar Hitzfeld are two of the best managers I ever played under," said the Scot, who played under the pair at Celtic and Borussia Dortmund.
"I absolutely loved playing under Martin," said Lambert.
"He could just get the best out of people. That was his biggest thing. His man-management was brilliant."
Lambert played under the Northern Irishman for five years between 2000 and 2005, helping the Glasgow club to win three Scottish Premier League titles and four domestic cups.
And he admits he sought the advice of O'Neill, who managed Villa for four years before resigning in 2010, before deciding to leave Norwich for Villa Park in the summer.
Lambert, who still refers to O'Neill as "gaffer", said: "Celtic at that time needed someone like Martin to drive them back up and he certainly did that. It's a huge club and thankfully he took it on.
"It was brilliant at Celtic in terms of the lads I played with. It was a fantastic era.
"If I ever need any advice off him I can just pick up the phone. But you learn from your own mistakes and I haven't spoken to him of late."
Meanwhile, Lambert says Villa must strengthen their squad after earning just six points from their opening nine games - the Birmingham club's worst start in 43 years.
"The squad needs to get bigger. Everyone has to have competition for places," he said.
"[The start] shows you are short in certain areas and you have to improve the squad which we will try to do."