The Celtics’ Kevin Garnett, Ray Allen and Paul Pierce (from left) have led Boston to the best record in the NBA.

AP / Branimir Kvartuc

The Celtics are home after a weeklong road trip that showed they are not as invincible as they appeared to be at the beginning of the season.

Sure, Boston still boasts the best record in the NBA, 43-12, but three losses in a row coming out of the All-Star break had to bring smiles to Detroit and Orlando, the other division leaders in the Eastern Conference. The Pistons have the second-best record in basketball, 42-15, only two games behind the Celtics with 25 to play.

So nobody can blame the Celtics for looking over their shoulders tonight as they welcome LeBron James and the Cleveland Cavaliers to the TD Banknorth Garden for their first game on the parquet since Feb. 13. What lies ahead for Boston in the next six weeks? First, a brief recap.

The Celtics went into the All-Star break having won five games in a row and seven of nine without center Kevin Garnett, who was recovering from a strained abdominal muscle suffered Jan. 25 when his old team, Minnesota, was in town. Garnett suffered the injury in the fourth quarter and missed four minutes while the team physician checked him out. Cleared to return, he played the last 1:51 and made a key steal at the end of Boston’s 87-86 triumph.

Those were his last minutes until after the break. The Celtics did all right without him, winning seven and losing only at Orlando and Cleveland.

Garnett joined Paul Pierce, Ray Allen and coach Doc Rivers in New Orleans for All-Star Weekend but did not play. He returned to the Celtics lineup two days later, played 20 minutes and scored four points in a 124-118 loss at Denver. He was his old self the next night against Golden State — 17 points, 15 rebounds, 30 minutes — but the Celtics still lost, 119-117, on Baron Davis’ 20-foot jumper with 0.3 seconds to play. His 19 points and 5 rebounds weren’t enough at Phoenix in Boston’s 85-77 loss. The Celtics shot a woeful 38.5 percent in that game.

Boston halted its three-game slide, its longest of the season, with a 112-102 victory at Portland. Garnett had 10 points and 7 rebounds, solid support to Pierce’s 30 points, 7 rebounds and 5 assists. And Monday night the Celtics routed the lowly Clippers, 104-76. Garnett had 11 points and 7 boards.

The Celtics center, the key to this resurgent season, is obviously healthy and must remain so for Boston to go deep into the playoffs in April and May. His defense — rebounds, blocked shots — leadership and focus are more important to this team than his scoring. Boston is allowing only 90.5 points per game, second in the league behind Detroit’s 90.28.

Allen is another who has to remain healthy. The veteran guard arrived from Seattle last summer with surgically repaired ankles and has missed only two games.

Ditto for Pierce. Boston needs his scoring.

All those supporting players who have performed so well must continue to do so. That’s the beauty of this team. Everybody contributes. Garnett, Allen and Pierce may be the New Big Three, but they and Kendrick Perkins and Rajon Rondo are the second-best five-man combination in the league, according to the Lenovo Stat, a plus/minus statistic that measures point differential when players are in and out of the game. According to the Lenovo Stat, Pierce is the top individual player in the NBA.

The only Celtics among the league leaders are Allen, who is fifth in free-throw percentage (171-for-188, .910), Garnett, 10th in field-goal percentage (336-627, .536), and Rondo, 14th in steals per game (1.71).

The chemistry on this team is solid, but basketball boss Danny Ainge is said to be interested in adding another veteran for the playoff run. Free-agent guard Brent Barry was in the mix and received an endorsement from Allen, a teammate in Seattle.

Now, back to what’s ahead. The playoffs, for sure. The Celtics have already guaranteed themselves a winning season — they could lose the rest of their games and still finish 43-39. Barring a major collapse, they should enjoy home-court advantage at least until the Eastern Conference finals.

The Celts have 27 games to play, 14 home, 13 away. Another long road trip looms next month, when they will visit Milwaukee, San Antonio, Houston, Dallas and New Orleans March 15 through 22. Six of their nine games in April will be on the road. If the Celtics can boast the best record in the NBA after their regular-season finale against the Nets April 16, then they just might have restored some of that invincibility they displayed in November and December.

mszostak@projo.com