Kawhi Leonard scored 20 points and grabbed 14 rebounds to lead the San Antonio Spurs to a surprisingly comfortable 107-86 victory over the Miami Heat and a 3-1 lead in the NBA Finals.

The Spurs put on a clinic on the offensive end for the second straight game at the American Airlines Arena in Miami, shooting 57 percent on Thursday night after making 59 percent of their attempts from the field in Tuesday's Game 3.

Leonard went 7-of-12 from the field, while point guard Tony Parker scored 19 points on 8-of-15 shooting and Australian reserve point guard Patty Mills shot 5-of-8 for 14 points.

The Spurs also got a big contribution from French power forward Boris Diaw, who littered the stat sheet with eight points, nine rebounds and nine assists.

San Antonio dominated the glass by a margin of 44-27 thanks in part to the 11 rebounds hauled down by veteran big man Tim Duncan, a key figure in all four of the Spurs' previous championships.

The Heat were ice cold from the field in the first half of the biggest game of their 2013-2014 season, scoring just 36 points to fall behind by 19.

Four-time NBA Most Valuable Player LeBron James scored 28 points and grabbed eight rebounds but received little help from his teammates.

The other two members of the Big 3, Chris Bosh and Dwyane Wade, scored just 12 points and 10 points, respectively.

Until Thursday night the Heat had not lost two consecutive playoff games since 2011, when they were defeated 4-2 by the Dallas Mavericks in the NBA Finals.

They smashed us," James was quoted as saying on NBA.com. "Two straight home games got off to awful starts. They came in and were much better than us in these last two games. It's just that simple."

The Spurs, who came achingly close to winning the championship last year before losing in seven games to the Heat, were careful not to give the two-time defending champions any bulletin-board material.

"I'm pleased that they performed as well as they did while we've been in Miami, and that's about as far as it goes," Spurs head coach Gregg Popovich said. "Now we've got to go back home and play as well or better."

Parker, who was the NBA Finals MVP in 2007, also was cautiously optimistic about the Spurs' chances of finishing off the Heat.

They're the two-time champs. They're a great team and there is still one more game. We have to win one more game."

To win the championship, the Heat must become the first team in NBA history to rally from a 3-1 NBA Finals deficit.

Game 5 of the best-of-seven series will be played in San Antonio on Sunday night, when the Spurs will try to win the fifth title in franchise history. EFE