Pitino said he wanted a day off to think about whether to return to the once-proud franchise he has been unable to revive in 3 1/2 years as coach and president.
But three newspapers - The Boston Globe, Boston Herald and The Providence Journal - said he had already decided to step down. ESPN.com reported that he reached a settlement Sunday with owner Paul Gaston on the remainder of a 10-year, $50 million contract they signed in 1997.
A woman who answered the phone at Gaston's home said he would not be available for comment. O'Brien did not speak to the media after Sunday's practice.
ESPN.com quoted Pitino as saying the team will release a statement announcing his resignation, but it did not say when. Pitino said he would receive two months' severance pay but would forfeit $22 million left on the deal, according to the Web site.
Pitino had hinted for 10 months that he would resign if the team did not improve this season. But as recently as November he promised to finish the 2000-01 season.
A 112-86 loss to Miami on Saturday night evidently changed his mind. He gave Paul Pierce a hug as he came out of the game, and spoke afterward as if his mind was made up.
"Sometimes change is good just for the sake of change when things aren't going well," he told the Herald. "It's heartbreaking to me, what's happened here. I love the Boston Celtics and I'll always be a fan.
"This organization has treated me like royalty since I came here. But you know, I've been going at this pretty hard now for 3 1/2 years and I haven't seen many results. It hurts, but life goes on and it will for the players and for the people in this organization."
Pitino told his players he was taking a day off from practice on Sunday and asked his wife to come down to Miami so they could discuss his next move.
"It's safe to say that I will have a decision after the day off," Pitino said.
The Celtics have lost 11 of their last 14 games, allowing 100 or more points in nine of those games. Pitino is 102-146 with the Celtics in 3 1/2 years, all of them losing seasons. This would be an unprecedented eighth consecutive losing season for a franchise that has won more NBA titles, 16, than any other.
"There's a lot of pressure when you put on a Boston Celtics uniform, or when you get the title o head coach of the Celtics. There's a lot of pressure in that job," captain Paul Pierce said after practice. "We really haven't fulfilled the expectations put on us.
"I just want him to make the decision that's going to make him happy. ... I don't know how happy he was lately."
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