The Boston Celtics are about to make history. They enter tonight’s Game 1 of the NBA Finals as the first underdog team to win 66 games and outscore their opponents by a margin of greater than 10 points.

In fact, only one team in NBA history has had 60-plus wins and a double-digit point differential and not won a title. That team was the 1972 Milwaukee Bucks, who went 63-19 and outscored their opponents by 11.1 points per game. They lost to the Los Angeles Lakers, who that year fielded one of the great teams in NBA history. The Lakers’ 69-13 mark was the best regular-season record until the Chicago Bull’s second title run, and they bested the Bucks’ differential that year with a 12.3 mark.

The Lakers team that plays the Celtics tonight is good — in fact, they are a superb team that would be runaway favorites in almost any other season — but I don’t think they are on Boston’s level this year.

Playoff basketball has become very personality-oriented, and this favors the Lakers enormously. Kobe Bryant isn’t just the MVP; he’s truly playing as if he enjoys being among equals, rather than a star with a supporting cast. Midseason acquisition Pau Gasol seems unstoppable; he moves well for a big man and his passing is stellar. Forward Lamar Odom is the perfect role player who puts up star-like numbers. Coach Phil Jackson is miles beyond his Boston counterpart Doc Rivers.

By contrast, all we’ve heard about how Boston is how they faltered against Atlanta and Cleveland, needing seven games to dispatch teams with negative point differentials. Boston shooting guard Ray Allen is a) looking his age or b) tired from playing too many minutes during the regular season. Doubts are even beginning to surface about Kevin Garnett’s greatness and whether the perennial All-Star is qualified for this moment.

There are good reasons to be wary about giving one month of mediocre play weight against six months of historically stellar ball. The Celtics’ play against the Detroit Pistons in the Eastern Conference Finals functioned as a loud reminder of this fact. The Celtics beat Detroit with suffocating defense and an efficient offense. Just to cite an instance, in Game 6 in Detroit, the Pistons led 70-60 late in the third quarter when Boston made a key adjustment. The Pistons had built their lead with perimeter shots. In response, Boston assistant coach Tom Thibodeau changed his defensive alignment so that the 6-foot-11-inch Garnett would roam the perimeter double-teaming the Pistons marksman. Detroit was held to 11 points for the remaining 13 minutes of the game, an 89-81 Celtic victory.

Aside from the occasional spectacular blocked shot, defense doesn’t come into play in the character-driven and highlight-clip-dependent presentation of sports news. Great defense is about five guys bearing down and forcing the other team to abandon one offensive option after another until someone — anyone! — has to heave a rainbow just before the 24-second shot clock expires. That’s Boston’s season in a nutshell. It wasn’t especially sexy, but as 66 wins attests, it was very effective.

Let’s look at the two teams’ regular-season matchups. On November 21 at TD Banknorth Garden in Boston, the Celtics raced out to a 22-point first-half lead en route to a 107-94 win. Their defense on Bryant was exceptional; Kobe scored 28 points but shot a poor 9-for-21. Only one other Laker, forward Vladimir Radmanovic, scored more than 13 points. As a team, the Lakers shot 42.2% from the field. They blamed the retro shorts they were wearing.

In the second meeting between the two teams, on December 30, at the Staples Center in Los Angeles, Boston laid it on harder, winning 110-91. The combination of Allen, Tony Allen, and James Posey held Bryant to a nightmarish 6-for-25 shooting. Defensively, whoever guarded Paul Pierce had a nightmare too; he scored 33, including four of eight from behind the arc.

Pundits who back the Lakers have been quick to dismiss these games because they occurred before Los Angeles acquired Gasol. The key thing to me is that Gasol didn’t replace a scarecrow like Kwame Brown, the player for whom he was traded, in the Lakers lineup; he replaced Andrew Bynum, who was having an All-Star-caliber season. Gasol represented an upgrade, but not a lineup overhaul.

I think that the six days off has done Boston more good than Los Angeles. The Lakers came away from their series against San Antonio in good shape. The time off has given Celtics guard Ray Allen some much-needed rest, and it’s given reserve guard/defensive specialist Tony Allen a chance to heal from his Achilles tendon injury. Initially thought to be doubtful, he is now likely to play some minutes during the series.

I hate to keep harping on this, but the list of 66-win ball clubs who have lost in the playoffs isn’t very long, and the Lakers aren’t good enough to add the 2008 Celtics to that list. I think Boston will win in six hard-fought games.

mjohnson@nysun.com