The starter's gun sounds Christmas Day on an National Basketball Association (NBA) sprint of a season that will reward cohesiveness and fitness in a compressed 66-game campaign that has the Miami Heat as clear front-runners.

Miami's 'Big Three' of LeBron James, Dwyane Wade and Chris Bosh came together as free agents last year and the nucleus made it to the NBA Finals before falling to the Dallas Mavericks.

After one season to work out the kinks, the Heat look ready to show they really have a hold on a league that used a five-month lockout of players to get a labor agreement that gave owners a bigger share of revenues and reshaped rules toward improving competitive balance.

James, who shied away from crunch-time responsibilities in the Finals, showed his commitment to claiming a maiden title by making an off-season pilgrimage to Houston for a tutorial on post moves from Hall of Fame center Hakeem Olajuwon.

In preparation for the season's December 25 start, teams held hurry-up training camps that coincided with a frenzied free-agent signing period that produced winners and losers.

The Heat index shot up, the Mavericks lost some firepower and the lowly Los Angeles Clippers created an instant rivalry with the Los Angeles Lakers and Kobe Bryant by adding premier point guard Chris Paul and other pieces.

Miami improved by adding sweet-shooting small forward Shane Battier, while Dallas may have taken a step back after losing center Tyson Chandler (New York Knicks), forward Caron Butler (Clippers) and back-up guard J.J. Barea (Minnesota Timberwolves) despite welcoming two-times NBA champion Lamar Odom to Texas.

A disgruntled Odom was ultimately traded by the Lakers, who had included the versatile forward in a trade offer to league-owned New Orleans for Paul, which was nixed by the NBA.

The Chicago Bulls, who reached the Eastern Conference final against Miami, added a potentially key piece in shooting guard Richard Hamilton, who could provide just the complement to point guard Derrick Rose, the NBA's reigning most valuable player.

While the impact of provisions on competitive balance is yet to be seen, the season figures to be ruled by teams that already know how to play together and can withstand the rigors of a schedule that includes three games in three days for all teams and stretches for some of five games in six nights.

Veteran-laden teams like the Boston Celtics, with their aging impact trio of Paul Pierce, Kevin Garnett and Ray Allen, could start fast but may wear down come playoff time.

The San Antonio Spurs could be in the same boat as Boston, ready to hit the hardcourt smoothly with a veteran trio of Tim Duncan, Manu Ginobli and Tony Parker, but eventually challenged to keep step with last year's Western Conference runners-up the Oklahoma City Thunder.

BIG UNKNOWN

The Thunder, with a young core of NBA scoring leader Kevin Durant and guards Russell Westbrook and James Harden leading the way, may be ready to reach the Finals.

The Knicks and Clippers are rounding into shape as possible contenders, but might need time to gel.

The Clippers, who won 32 games last year and have exceeded the .500 mark once in the last 19 years, have a new look.

Besides adding premier point guard Paul, they have also welcomed former Mavs forward Butler and veteran guard Chauncey Billups to a young squad that boasts former overall number one pick Blake Griffin and talented center DeAndre Jordan.

Chandler brings a defensive presence down low for the Knicks, whose high-scoring duo of Carmelo Anthony and Amar'e Stoudemire continue to blend their skills after half a season together in New York.

One big unknown factor in the season is the fate of Dwight Howard, the powerful center of the Orlando Magic, who is in a lame duck season with free agency looming.

Viable suitors for Howard include the Lakers, Mavericks and the New Jersey Nets, whose imminent move to Brooklyn gives them appeal as a true second New York City team with outstanding point guard Deron Williams already in place.