For most of Monday’s 4-hour, 10-minuteU.S. Open men’s final, the spectacle on Arthur Ashe Stadium felt more like a heavyweight prizefight than a tennis match, with Novak Djokovic and Rafael Nadal trading full-body blows with their rackets.

But the top-seeded Djokovic landed the more punishing hits, pummeling Nadal, the tournament’s defending champion, 6-2, 6-4, 6-7 (7-3), 6-1, to win his first U.S. Open championship after finishing as the tournament’s runner-up in 2007 and 2010.

With the victory, Djokovic extended his record this incomparable season to 64-2.

At 24, the Serb has now won three of the sport’s four majors, adding the U.S. Open to a portfolio that includes the 2008 and 2011 Australian Opens and Wimbledon in July, where he also dethroned Nadal.

And he won this U.S. Open by defeating Roger Federer and Nadal, the players who had a chokehold on the No. 1 and 2 rankings for four years, in the span of three days.

Novak Djokovic of Serbia poses with the trophy after winning the men's championship match. (Charles Krupa/Associated Press)

Djokovic fell flat on his back on the court as flashbulbs erupted after ripping a 55th and final forehand winner to close the match, having needed medical help to slog through the final set, ailing from a sore lower back, painful ribs and leg cramps.

“I had to go for my shots, and I did,” said Djokovic, who summoned enough firepower despite his ailments to win five of the final six games against the stronger, fitter Nadal.

As the match made clear, Nadal, 25, has yet to figure out a solution to Djokovic, now 6-0 against him this year, no matter how much energy he expends on court.

Before a rapturous crowd of 24,712, Nadal mounted another physically wrenching, fully committed effort against Djokovic Monday. Once again, he lost.

But the Spaniard said afterward that he felt he had taken a step toward closing the gap, forcing himself to be more aggressive in his tactics.

“I go back home knowing I am on the way,” said Nadal, who still holds a 16-13 record against the Serb. “You know, I like to fight. I want to enjoy this battle against him. Six straight losses — for sure, that’s painful. But I’m going to work every day until that changes.”

There was an unrelenting rhythm to the match, and it exacted a harsh toll on both men, who ran themselves to exhaustion contesting 20- and 30-stroke rallies that defied description in their athleticism.

Rafael Nadal of Spain reacts against Novak Djokovic of Serbia. (Nick Laham/Getty Images)

More than one factor made the difference.

Remarkably quick and agile on court, Djokovic retrieved balls that looked impossible to reach.

And though Djokovic’s ability to cover the court makes him an exceptional defender, he’s instinctively attack-minded, delighting in coming forward to finish points with a volley or cruel angle.

He handled Nadal’s topspin-slathered balls with no problem; and he sent them back at twice the pace with a bullet’s flat trajectory.

Moreover, Djokovic blasted big serves when he needed and broke Nadal’s serve 11 times.

“That changed a lot the match,” Nadal conceded of his serve, which was uncharacteristically ineffective. He managed just two aces while double-faulting twice.

And Nadal compounded his challenge by playing nearly the entire match from behind the baseline, pouring every ounce of energy into shots that landed at midcourt — almost inviting Djokovic to come in and attack.

Nadal jumped to a 2-0 lead to open the match, but Djokovic reeled off six successive games, crushing his groundstrokes and pouncing on Nadal’s second serve to take the opening set.

The second set was a replay of the first. Nadal broke early for a 2-0 lead, then retreated to counter-punching mode when his forehand lost its bearings, along with his first serve.

With Djokovic leading two sets to none, Nadal had a chance to take a 5-3 lead in the third set, with the Serb facing break point. A 31-stroke rally followed, and Djokovic closed with a backhand winner down the line. A natural showman, he turned to the crowd, arms wide, seeking applause.

The show of praise rained down on both men for their breathtaking effort. “One of the greatest points you’ll ever see at a U.S. Open final,” four-time U.S. Open champion John McEnroe gushed from the CBS broadcast booth.

A tiebreak was needed to settle the third set. And Nadal, facing straight-sets elimination if he faltered, capitalized on two gaffes by Djokovic for a 4-1 lead, then ripped a forehand winner to go up 5-1.

Nadal looked as if he could push on to a fifth set, while Djokovic called for a medical timeout to get treatment. After whatever ailed him was kneaded out, the Serb stormed to the finish, taking more risks than ever in a frantic attempt to shorten the points and close the match before he gave out entirely.

“I knew I’m not physically there,” Djokovic said. “I had to take chances.”

It was a thrilling ending to a tournament that was marred by rain delays, scheduling controversies, a Grand Slam-record number of injury-induced retirements and Serena Williams’s abusive tirade at the chair umpire following a controversial penalty in the women’s final.