At the Break, Challengers Forming a Line : NBA: At halfway point of season, a half-dozen teams loom as contenders to dethrone two-time defending champion Detroit.

A half-dozen teams -- defending champion Detroit, 1990 finalist Portland, 1980s powers Boston and the Los Angeles Lakers and superstar-dominated Chicago and San Antonio -- loom as championship threats at the NBA All-Star break.

The Trail Blazers, who lost to the Pistons in five games in the Finals last June, held the NBA’s best record from the opening weeks, winning their first 11 games and maintaining a plus-.800 pace through the midway point.

Portland is outscoring its opponents by an average of 10 points a game, and only two teams in NBA history -- the 1972 Lakers and the 1971 Milwaukee Bucks -- finished with a double-figure point differentials. Both of those teams rolled to NBA championships.

“We’re a much more consistent team this season,” Blazers coach Rick Adelman said., “and there are three reasons for that.

“One is the addition of Danny Ainge, who coming off the bench gives us scoring on the second team. Then there’s the continuing development of your young players. Finally, we’ve had a year of playing together. A year ago, we had six new players, and it’s only natural that they should play better.”

Detroit held first place in the Central Division at the break despite the loss of captain Isiah Thomas to wrist surgery that will sideline him until at least May.

But with Thomas healthy, the Pistons lost nine of their first 12 games in December before righting themselves with an 11-game winning streak.

“This is my 10th year in the league and teams and individuals have never played harder against us,” Thomas said during the slump.

“It’s amazing how we hear the other team always saying that it was their best game of the year,” coach Chuck Daly said.

The Celtics, a moribund team that lost in the first round of the playoffs last season, rediscovered the winning touch with an infusion of younger, faster players to go with Larry Bird, Kevin McHale and Robert Parish.

“I didn’t know if I’d ever have this much fun again,” McHale said. “Back around 1987-88, we became a plodding, walk-it-up team. Guys were beating on our backs. Now we have so much freedom, we feel revitalized. I think the young guys do that to you.”

Guards Reggie Lewis, Brian Shaw and Dee Brown headed the Celtics’ youth corps. Perhaps the best example of Boston’s rejuvenation came in its 152-point performance against Indiana on Dec. 26, the Celtics’ highest point total in a regular-season game in 20 years.

Boston was 27-5, its best start since 1973, before a back injury to Bird started a run of six losses in seven games. Nevertheless, rookie coach Chris Ford became the coach for the East team in the All-Star game.

In Chicago, this again was supposed to be the year that Michael Jordan’s scoring burden with the Bulls was supposed to lessen as younger players and veterans blended in with his awesome talents.

Wrong.

Jordan, sixth in the league in scoring three weeks into the season, was back at No. 1 at the break, putting him in position for his fifth consecutive scoring title. The Bulls, with injuries to Thomas and Bird threatening the Pistons and Celtics, still have a good chance to go into the Eastern playoffs with the homecourt advantage.

Chasing Portland in the West were the Lakers and Spurs.

Los Angeles, winners of five titles in the 1980s, had the wolves snapping at its heels after a 2-5 start, but an NBA-best 16-game winning streak had them talking about catching the sprinting Trail Blazers.

Magic Johnson and James Worthy are deserving All-Stars again, Byron Scott has redisovered his shooting touch and second-year center Vlade Divac appears to be more comfortable in the middle.

“We’re playing championship-caliber basketball right now,” Johnson said. “Earlier in the season, we were playing at playing basketball. We weren’t really playing basketball.”

Better performances from bench players A.C. Green, Terry Teagle and Mychal Thompson could make the Lakers formidable challengers at playoff time. Green lost his starting spot to free-agent signee Sam Perkins.

“The one disappointment has been that our bench hasn’t played well,” Lakers general manager Jerry West said, “but they’re starting to. If they do play better, we are a very, very dangerous team.”

San Antonio was the last NBA team to lose consecutive games in the first half of the season as David Robinson, along with Jordan, became a midseason MVP favorite with magnificent play at center. Robinson leads the league in rebounding and blocked shots and is averaging more than 26 points.

Lower in the standings, Milwaukee and coach Del Harris startled the experts who picked the Bucks for the second half of the Central Division by starting 25-8, including 18-0 at home, before falling behind the onrushing Pistons and Bulls.

“The remarkable story of the whole thing is that Del did exactly what he said he would do; rebuild the team without suffering a losing season or two,” Golden State’s Don Nelson said. “I give him all the credit in the world.”

The Bucks were sparked by the backcourt trio of Alvin Robertson, Jay Humphries and Ricky Pierce.

“It’s one of the best three-man rotations in the league,” Cleveland general manager Wayne Embry said.

Another surprise was the inspirational play of Bernard King, averaging 30 points six years after a serious knee injury nearly ended his career. He made the All-Star team for the first time since 1985.

“Being an All-Star again is a dream come true,” a tearful King said after his selection.

He scored 52 points against Denver and followed that up with a 49-point performance at Madison Square Garden, proving conclusively that the New York Knicks gave up on him too soon.

“He scores so much, I don’t even keep track (of how many points he scores) anymore,” Bullets guard Darrell Walker said. “His jump shot has improved so much in the last two or three years. He’s an inside-outside threat now. He’s just very tough to guard.”

The Denver Nuggets surely attracted more attention than any team ever that was 11-30 at midseason.

They were the laughingstock of the league for two months, not only starting 6-28 but allowing the opposition to score without opposition.

But sparked by the play of tiny Michael Adams, the Nuggets started gaining respect by winning eight of 10 games, including six straight.