BOSTON – Kevin Garnett craned his long neck up at the Celtics’ 16 championship banners above his new home court and saw that the last one was dated way back in 1986.

“’86, huh?” the 10-time NBA All-Star said.

“21 years ago,” a reporter told him.

To which Garnett quickly replied: “21s a good number.”

A good number to end the drought on, and any team needs some luck – whether it’s avoiding injuries or getting a key foul call – to win a title, but Boston needs a lot less of it now.

With the 6-foot-11 Garnett joining forward Paul Pierce and guard Ray Allen as the team’s new Big Three, the Celtics went from the team with the second worst record in the NBA to instant contenders in the mediocre Eastern Conference.

“I thought this is probably my best opportunity to win a ring,” Garnett said after being obtained Tuesday from the Minnesota Timberwolves in a 7-for-1 deal – the most players traded for one player in NBA history. “It was a no-brainer.”

Minnesota, which missed the playoffs the last three seasons, adopted the Celtics now abandoned policy of rebuilding with youth. Of the five players they received, four – forwards Al Jefferson, Ryan Gomes and Gerald Green and guard Sebastian Telfair – are 24 or younger. The fifth is 34-year-old center Theo Ratliff.

“We gave up a lot,” Celtics executive director of basketball operations Danny Ainge said. “Too much? Time will tell.”

The Celtics also gave up their first-round draft pick in 2009, unless it is among the top three, and returned Minnesota’s conditional first-round draft pick obtained in January 2006 when they sent Ricky Davis to the Timberwolves for Wally Szczerbiak. Minnesota also received cash considerations.

“I’m confident the (Minnesota) fans know that this is something we needed to do to get better in the long run,” Timberwolves owner Glen Taylor said.

The key for Minnesota is Jefferson, whom the Celtics were reluctant to part with. He had a breakout season in 2006-07, his third with Boston, when he averaged 16 points and 11 rebounds.

“I’ll always have a special place in my heart (for Minnesota), but I think at this point in my career I can’t do young,” said Garnett, who spent all 12 of his seasons there, “and I think that you need veterans to win.”

The outstanding scorer, rebounder, defender and passer signed a multiyear extension to the contract that had one year and an option year left. Ainge wouldn’t reveal its length.

The Celtics were 24-58 last season and have won three playoff series in Pierce’s nine years.

“I feel like a rookie again,” Pierce said. “I’m just excited. … It’s been hard on me the last couple years just trying to stay motivated.”

The last Celtics championship was the third with the Big Three of Larry Bird, Kevin McHale and Robert Parish. Ainge was on that 1986 team. Twenty-one years later he and McHale orchestrated the blockbuster deal. McHale is the Timberwolves vice president of basketball operations.

“These guys will never be the Big Three until they win,” Ainge said of his new trio. “They know nothing has been accomplished by this team at all.”

But, he acknowledged, “This is going to be a lot of fun.”

The trade left the Celtics with a thin roster and needing veteran backups at point guard and center. Coach Doc Rivers said it would be “fantastic” to get free agent Dikembe Mutombo.

The starting lineup includes second-year pro Rajon Rondo at point guard and Kendrick Perkins at center. Only four other players are under contract.

“Clearly, we need a little bit more help just to shore up the bench,” Rivers said, “but it’s sure better talking about shoring up our bench than shoring up our starting lineup.”

Garnett was the fifth player drafted in 1995, coming out of Farragut Academy in Illinois and starting a trend of players skipping college.

He has averaged more than 20 points and 10 rebounds for each of the last nine seasons. He is among five players in NBA history with at least 19,000 points, 10,000 rebounds and 4,000 assists. The others are Wilt Chamberlain, Kareem Abdul-Jabbar, Karl Malone and Charles Barkley.

Slightly over two months ago, the Celtics got the fifth pick in the draft lottery. They had the second best chance to get the first pick and a shot at Greg Oden of Ohio State or Kevin Durant of Texas.

Getting Garnett is much better than winning the lottery, Rivers said.

“There’s no doubt about that,” he said. “It’s great to have hope with the young and know that someday they may be good. But we’re not talking about potential today.”

They were talking about achievement.

Garnett was the league’s MVP in 2003-04 and its leading rebounder each of the last four seasons. Allen is a seven-time All-Star and Pierce has been on five All-Star teams. Teams will have to “pick their poison” when defending them, Allen said.

But Allen is 32, Garnett is 31 and Pierce is 29.

“These guys have all tried to carry a franchise,” Ainge said. “If they can just have a little bit less burden, spread the wealth a little bit more, there’s no reason why they can’t prolong their careers.”

Ainge talked with Garnett before the draft, but he preferred other destinations. So the Celtics traded with Seattle for Allen on draft day, knowing it would make them more attractive.

“The whole situation changed for me” with that trade, Garnett said.

Suddenly, the Celtics are less attractive to opponents.

“I remember going back to the days when this organization battled against the Lakers and every time (teams) came in here they were afraid,” Allen said. “I think those are the days we’re headed back to.”