BOSTON (AP) – Jim O’Brien, who walked away from his job as head coach of the Boston Celtics this week, said he resigned because he differed with his boss over whether to fashion a strong defensive team, or one that emphasized offensive firepower.

O’Brien, in his three years as head coach, had an unwavering commitment to defense.

“I didn’t think the relationship was a bad relationship,” O’Brien said Wednesday in his first public comments since he quit on Tuesday. “I thought it was just what (Ainge) said it was about – philosophical differences. He believes in a certain way of achieving (NBA championship) banner 17. I told you what my thoughts were strategically (with defense first and foremost). I respect that he is in charge of the whole thing. He’s executive director. He had every right to expect people to share his vision. I thought I could, and I guess at some point in time I realized he would be better off with somebody else.

“At the end of the day, I just felt if he’s going to grow this exactly the way he wants, he needed followers that believed in how he was going to grow. In good conscience, I could not tell him that I was going to be that guy.”

O’Brien stepped down with his team in a 2-5 slump with players Ainge brought in since taking over last May 9 as director of basketball operations. The Celtics lost to Detroit 106-103 on Wednesday under his replacement, former assistant coach John Carroll.

“I prefer to have guys who are ready to smack you in the mouth if you try to bring the ball to the rim,” O’Brien said. “I value guys like that. I have a real strong opinion that that’s the way it should be.

“Danny, basically, wants guys who can score the ball, and that’s fine. It’s just not a relationship that was made for the long run.”

Ainge, who played on two Boston championship teams, had given O’Brien a two-year extension through 2005-06.

The hiring of Ainge at the end of last season was the first of many changes for the Celtics, who have just three active players – Paul Pierce, Mark Blount and Walter McCarty – who were on the team last season.

Ainge traded Antoine Walker to Dallas on Oct. 20, then sent veteran team leaders and defenders Eric Williams and Tony Battie to Cleveland on Dec. 15.

O’Brien said he agreed with Walker trade, but was very much against the Cleveland deal.

“It was difficult to lose guys who were part our success, but I was a big boy,” O’Brien said. “I needed to get past that.”

O’Brien was an assistant when he became head coach on Jan. 8, 2001, after Rick Pitino stepped down. O’Brien led the Celtics to a 139-119 regular-season record and to the Eastern Conference finals and semifinals the past two seasons.

AP-ES-01-29-04 0819EST