WALTHAM, Mass. (AP) Danny Ainge came to Boston and started shipping out veterans and suggesting who should play. Celtics coach Jim O'Brien didn't agree with that style, so on Tuesday he left, too.

O'Brien resigned midway through his fourth season and was replaced on an interim basis by assistant coach John Carroll, who Ainge said would remain for the rest of the season.

``This isn't exactly how I thought this day would end,'' said Ainge, who was named executive director of basketball operations last May 9.

He said O'Brien offered his resignation Tuesday morning at one of their regular meetings to discuss their philosophical differences. Assistant Dick Harter was let go.

A call placed to O'Brien's agent, Lonnie Cooper, wasn't returned after the resignation was announced at an evening news conference attended by Ainge and three of the Celtics owners at the team's practice facility.

Carroll will remain the team's coach for the rest of the season, Ainge said.

Ainge wanted to build a younger, more offensive team. O'Brien relied on veterans who were strong defenders and team leaders. So when two of those veterans, Eric Williams and Tony Battie, were traded to Cleveland on Dec. 15, O'Brien tried to put a good face on his disappointment.

``I'm losing some guys that I really care a great deal about,'' O'Brien said at the time. ``But the trade is on, and this is who we have, and I will welcome our three new players with open arms.''

Ainge said Tuesday that O'Brien didn't fully agree with the deal but that the coach ``was 100 percent on board'' with the trade of Antoine Walker to Dallas on Oct. 20. Ainge also said that it was his prerogative to make suggestions about playing time, though O'Brien did not have to follow them.

Walker's departure left Paul Pierce as Boston's only major offensive threat. That changed when Ainge obtained Ricky Davis in the Cleveland deal, but the team's defense has declined since then.

The Celtics lost five of their last seven games, including a 110-91 setback at New Jersey on Sunday. Boston trailed by 17 at halftime and sank just 36 percent of its shots for the game. In those last five losses, Pierce, who hasn't gotten much offensive help, made just 27 percent of his shots.

Boston is 22-24 and in second place in the weak Atlantic Division. Ainge was more willing than O'Brien to rebuild the team into a consistent contender even if it meant a short-term setback.

``The philosophical differences, I thought, were much smaller than Jim thought,'' said Ainge, who denied that he forced O'Brien to resign. ``I was willing to work through those. Jim did not see that long-term vision that I saw.''

So O'Brien decided to step down.

``He was not sure he's the man for that job,'' owner Wyc Grousbeck said. ``He didn't want to take our money and our time under false pretenses.''

He and Ainge praised O'Brien.

The only players remaining from last year's team are Pierce, Mark Blount, Walter McCarty and Vin Baker, who has been suspended indefinitely for failure to comply with his aftercare program for alcohol use.

O'Brien became interim head coach on Jan. 8, 2001 after Rick Pitino stepped down, then signed a multiyear contract on April 24, 2001. Ainge gave him a two-year extension through the 2005-06 season.

``I've said many times, 'There's not a harder working coach in the NBA.' And I still believe that,'' Ainge said.

O'Brien was associate coach to Pitino at Kentucky from 1994 through 1997 then became his assistant in Boston starting in the 1997-98 season.

He led the Celtics to a 24-24 record in his first season then took them to the playoffs the next two years. They reached the Eastern Conference finals in 2001-2002 and the conference semifinals last season, losing both times to New Jersey.

O'Brien's resignation came one day after Nets coach Byron Scott was fired with his team leading the Atlantic Division with a 24-22 record. New York, Miami and Orlando _ all Atlantic teams _ also have new coaches this season.

Carroll became a Celtics assistant in 1997 after serving as an advance scout for Orlando the previous season and for Portland the season before that. From 1998 through 1995 he was head coach at Duquesne.

``He's done a great job as an assistant coach to this point,'' Ainge said. ``John Carroll is the man for the rest of the year.''

The Celtics' next game is at home on Wednesday night against the Detroit Pistons, who are second in the Central Division with a 29-16 record.