BOSTON - Antoine Walker is coming back to Boston.

The Celtics’ former captain, who was traded away before the 2003 season, was reacquired on Thursday in a deal that will send Gary Payton, Tom Gugliotta and Michael Stewart to Atlanta. Boston gets an undisclosed amount of cash in the deal and gives up one of its two first-round draft picks in either 2005 or ’06.

“I think Antoine improves our team right now, and it doesn’t jeopardize our future,” Celtics basketball boss Danny Ainge said. “We’ve been in discussions with Atlanta for about a month. They were looking at taking some of my pieces for the future. Today the price came right and the risk came low.”

Everyone involved in the trade has a contract that expires after this season, including Walker’s deal that is paying him $14.6 million. Ainge said discussions of an extension would wait until the summer and were not a part of the trade.

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The Celtics lead the Atlantic Division by percentage points over the Philadelphia 76ers, but both teams entered Thursday night one game below .500 and in danger of missing the playoffs if they can’t win the division. The Sixers have dramatically reshaped their roster, acquiring Chris Webber, Jamal Mashburn and Rodney Rogers in the past two days.

“We think the addition of Antoine Walker brings needed presence under the boards and a proven winner back to Boston,” Celtics owner Wyc Grousbeck said. “We are making a playoff push and are focused on becoming a better, bigger team down the stretch.”

The Hawks haven’t made the playoffs since 1999 and have the league’s worst record (10-43) in the second year of their latest rebuilding effort. But general manager Billy Knight wanted to bring in as many young players as possible, and Walker wasn’t part of the team’s long-term plans.

The Hawks are carrying four rookies who were drafted last summer, including first-rounders Josh Childress and Josh Smith.

“I’ve put the organization in a tough spot,” Knight said. “I’ve put (coach) Mike Woodson in a tough spot. And it’s tougher now, because I traded away his leading scorer and rebounder.”

Knight said he had not spoken with Payton but wasn’t worried about the guard reporting to the Hawks, whose next game is Friday night at Portland. Payton was reluctant to go to Boston after being traded by the Lakers.

By trading Payton, a nine-time all-star, and Jiri Welsch in a separate deal, the Celtics improve their rebounding but leave their ballhandling in the care of Marcus Banks, Tony Allen and Delonte West — three players who have a total of one year of experience. A natural forward, Walker can also bring the ball up.

The move reunites Walker with Paul Pierce, a duo that took Boston to the 2002 Eastern Conference finals and gave the franchise its best years since the Big Three era of Larry Bird, Kevin McHale and Robert Parish — along with Ainge — won the last two of a record 16 NBA titles. It also reunites him with Ainge, who traded him away months after taking over in Boston.

Ainge said he spoke to Walker on Thursday and any bad feelings are in the past. Walker is trying to get to Salt Lake City in time for Friday night’s game, Ainge said.