MIAMI » Here they are again, back on the brink of a championship.

It slipped away from the San Antonio Spurs last year, but it would take something special — historic, actually — to stop them now.

The Miami Heat would have to make the biggest comeback in NBA Finals history.

"They’re the two-time champs, they’re a great team, and there is still one more game," Spurs guard Tony Parker said. "We have to win one more game."

Kawhi Leonard had 20 points and 14 rebounds, and the Spurs routed the Heat again, winning 107-86 on Thursday night to open a commanding 3-1 lead.

The Spurs can win their fifth NBA championship with a victory at home in Game 5 on Sunday and avenge their seven-game loss to Miami last year. They have three chances, and the way they’re dominating the Heat, they might need just one.

"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 coach Gregg Popovich said. "Now we’ve got to go back home and play as well or better."

LeBron James had 28 points and eight rebounds, but Dwyane Wade was just 1 of 10 through three quarters and finished with 10 points.

"They smashed us," James said. "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."

No team has overcome a 3-1 deficit in the finals, and the way the Heat were outclassed twice on their home floor makes it hard to imagine the two-time champions being the first.

"We put ourselves in a position where it is about making history," James added.

Parker added 19 points, and Tim Duncan had 10 points and 11 rebounds for the Spurs, who shot 57 percent from the field and are hitting 54 percent in the series.

The Spurs lost twice in Miami to end last year’s finals, their only defeat in the championship round. They won their two games in South Florida this time by a combined 40 points.

San Antonio’s surprising dominance has Miami on its heels, and unless Miami can figure things out quickly, the Heat’s two-year championship reign will come to an abrupt end.

If this was the last home game of the season in Miami, it looked and sounded nothing like the ones to end the last two years, which featured confetti falling and trophies raised. This one had the unfamiliar sound of boos late in the first half and a chant of "Go Spurs Go!" with under 3 minutes left from the San Antonio fans who remained long after many of Miami’s had bolted.

A Heat win Sunday would force a Game 6 in Miami Tuesday.

The Heat had followed their last 13 postseason losses with a victory, but now at the end of a fourth straight season that has gone the distance, they might be out of gas. Miami seemed to lack the energy — or maybe effort — to defend San Antonio’s precision ball movement for the full 24 seconds, and time after time the Spurs ended up with a shot from somebody who didn’t have a defender nearby.

Not quite as sharp as when they shot a finals-record 75.8 percent in the first half Tuesday night, the Spurs were still plenty good enough to open another huge lead by halftime, and they withstood every attempt Miami made to make a run.

"We were expecting a reaction from them but we were ready for it, so we just did the same thing," Spurs forward Boris Diaw said.

The Spurs knew their defense had to be better, realizing their once-in-a-lifetime, 19-for-21 start in Tuesday’s 111-92 Game 3 victory covered the fact that they allowed Miami to make more than 50 percent in the game.

They held Miami to 35 percent in the first half.

"They played great and I can honestly say I don’t think any of us were expecting this type of performance," Heat coach Erik Spoelstra said.

San Antonio blew the game open late in the second quarter with seven straight points, capped by Leonard’s soaring follow dunk that made it 55-33.

James, who battled cramps in Game 1, left the court and briefly returned to the locker room midway through the first quarter Thursday. But he had 10 quick points in the third quarter to bring Miami within 13, but San Antonio pushed it to 81-57 after three and never looked back.

Notes: Under Popovich, the Spurs have won 15 of the 18 best-of-seven series in which they led 2-1. … The Heat hadn’t lost back-to-back games in the playoffs since dropping three straight against the Boston Celtics in the 2012 Eastern Conference finals.