(Reuters) - NBA Commissioner David Stern vowed to punish the San Antonio Spurs for sending Tim Duncan, Tony Parker, Manu Ginobili and Danny Green home early rather than play in Miami on Thursday against NBA champion Heat.

Despite missing several top players, the Spurs nearly shocked the Heat in the nationally televised game, leading 98-93 with 2:14 left, before Miami's big guns went on a 12-2 run to claim a 105-100 victory.

Miami improved to 11-3 and the Spurs slipped to 13-4.

With the second-placed Spurs set to take on Southwest Division-leading Memphis Grizzlies in San Antonio on Saturday, coach Gregg Popovich decided his group of veterans could use an extra day of rest at home after their hectic road stretch.

Stern lashed out at the move.

"I apologize to all NBA fans," Stern said in a statement. "This was an unacceptable decision by the San Antonio Spurs and substantial sanctions will be forthcoming."

The Spurs, who had won the first five games of their six-game road trip ending in Miami, were left with just nine active players against the Heat but gave Miami all they could handle.

"Everybody has to make decisions about their schedule, about players playing and back-to-backs and trips and that sort of thing," Popovich told reporters before the game.

"In our case, this month we've had 11 away games, after tonight. We've had an eight-day trip and a 10-day trip, and we're ending it with four (games) in five nights here. I think it'd be unwise to be playing our guys..."

A three-pointer by Ray Allen put Miami ahead 100-98 with 22 seconds left and free throws by LeBron James, Dwyane Wade and Allen secured the win.

Guard Gary Neal led the Spurs with 20 points and Tiago Splitter added 18 points as five San Antonio players scored in double figures.

James scored 23 points with seven assists and four steals, while Allen poured in 20 points in just 27 minutes on court and Wade added 19.

"It doesn't matter who's out on the floor, everybody's in the NBA for a reason," James said about the Spurs' makeshift lineup. "We don't underestimate anyone."

(Reporting by Larry Fine in New York, Editing by Peter Rutherford)