BOSTON — Doc Rivers received a contract extension giving him three more years as coach of the Boston Celtics yesterday after leading them to an NBA title one year following the second worst season in team history.

Rivers' contract, which had one year left, was extended through the 2010-2011 season at an annual salary of about $5.5 million, according to a person familiar with the deal who spoke on condition of anonymity because the team does not release contract details.

Rivers coached the Celtics to their NBA record 17th championship and their first in 22 years in his fourth season as coach. Their 66-16 regular record was the best in the NBA and third best in club history.

They were 45-37 in his first season but just 24-58 in his third. The one year 42-win turnaround from that is a league record.

"He can handle the pressure of having to go through losses. He was extremely even keel in the worst periods," Steve Pagliuca, an owner and managing partner of the team, told The Associated Press.

The fortunes of the team turned around when it obtained guard Ray Allen from Seattle and forward Kevin Garnett from Minnesota in separate trades before last season.

The deals cost them several young players they had stockpiled, including Al Jefferson, who was developing into an outstanding forward.

But Rivers proved as adept at leading veteran stars as he was at teaching inexperienced players. That was one major reason the Celtics decided to extend his contract.

"We felt that Doc did an outstanding job ever since he's been here with the young players and transforming the veterans we have into a championship team," Pagliuca said.

The Celtics lost forward James Posey to free agency but are optimistic about draft choices J.R. Giddens, a guard, and Billy Walker, a forward. The entire starting lineup of Garnett, Allen, Paul Pierce, Rajon Rondo and Kendrick Perkins returns.

"Doc molded a championship team last season through his leadership and we are confident that he is the man to lead this franchise on the court now and in the future," general manager Danny Ainge said in a statement.

In his four seasons as coach of the Celtics, Rivers is 168-160.

"He's extremely team oriented in everything that he does so he wants the focus to be on the players," Pagliuca said. "He's a great teacher of young guys and because he was an NBA All-Star and very well respected point guard player, he's had an unbelievably good rapport with the superstars. He knows how to handle them and he knows how to really bring young players along."