BOSTON – When the Boston Celtics built a new practice facility, they surrounded the court with their 16 NBA championship banners and left a blank space for No. 17.

The message was a bit too subtle for Doc Rivers.

The Celtics coach turned a spotlight on the empty spot on the wall at the beginning of this season so there would be no doubt about the team’s goal.

“They can turn that thing off now,” guard Ray Allen said early Wednesday morning, his left eye still red from the first-half face-raking and the postgame champagne spraying that accompanied Boston’s title-clinching, 131-92 victory over the Los Angeles Lakers.

Allen returned to the floor after getting poked in the eye and scored 26 points, including an NBA record-tying seven 3-pointers, Kevin Garnett had 26 points with 14 rebounds and finals MVP Paul Pierce scored 17 with 10 assists on Tuesday night as the Celtics smoked the Lakers like one of Red Auerbach’s legendary victory cigars.

A year after winning just 24 games, then drawing bad luck in the draft lottery, the Celtics completed the most dramatic turnaround in NBA history with a Game 6 blowout that was equally impressive.

It was the 17th title for the league’s most-decorated franchise, but it was the first for Pierce, Garnett and Allen; for Rivers, after nine full seasons as a coach and 13 as a player; and for the owners who named their group Banner 17 when they took over in 2002 and now have to consider whether they set their sights too low.

“If I changed it I would change it to Banner 20 to set the right tone,” owner Wyc Grousbeck said in an e-mail on Wednesday. “But Red always said the first one was his favorite, and in honor of our first one we are going to stay with Banner 17.”

It was also the first title for Celtics general manager Danny Ainge also since hanging up his sneakers and putting on a suit.

“I just feel happy for the players,” said Ainge, who won twice as a Celtics player in the 1980s. “They put so much time and hard work into it.”

So did Ainge.

His was an oddly timed hire, in the middle of the 2003 playoffs, and he immediately concluded that the team competing for a spot in the Eastern Conference finals wasn’t good enough to go much further. He began dismantling the roster, acquiring draft picks, prospects and expiring contracts without apparent regard to how they would fit together.

The Celtics did what they could last season to improve their chances in the draft lottery, but they landed the worst-case fifth pick in a two-star draft. Unable to convince Garnett to come to a struggling team, Ainge traded the No. 5 pick for Allen.

Suddenly, the Celtics’ prospects look a whole lot better to Garnett.

After signing him to a contract extension that would keep him in Boston through 2012 – there was no deal without the extension – Ainge made an unprecedented 7-for-1 trade with Minnesota GM Kevin McHale to complete the new Big Three that won it all in its firs try.

“It’s a team that’s easy to fall in love with,” Ainge said after the celebration. “They have a lot of guys who are real caring people, that care for one another genuinely. They play together and play hard and I’m glad to be a part of it.”

Ainge and Rivers have all five starters signed for two more seasons, and all but Allen are in the fold for 2010-11. Sixth man James Posey is the key free agent, though midseason acquisitions P.J. Brown and Sam Cassell are also unsigned for next year.

The bigger question is whether the Big Three, so hungry after a decade of watching other teams celebrate, can come back and do it again.

The original Big Three of Larry Bird, Robert Parish and McHale – the same McHale who handed Garnett to his former teammate – won three times in the 1980s, reaching the finals four years in a row from 1984-87, but never repeated.

“I know what it means to win a championship as a Celtic, and the place championships hold in the history of the franchise,” Bird, now an executive with the Indiana Pacers, said Wednesday. “I’m also pleased for Danny Ainge, Doc Rivers and his staff, knowing where they were last year and then making the decisions to put them in position to win the team’s 17th title.”