There was a time when the thought of Novak Djokovic breaking down in a battle of endurance seemed impossible.

For so long the relentless Serb has been the definition of durability and stamina in the men’s game, yet - in pulsating US Open  final - he was left to wilt by the brilliance and power of Switzerland’s Stan Wawrinka - who won his third Grand Slam title in New York.

The 31-year-old, who has lived in the shadow of the great Roger Federer for most of his career, has now won three of tennis’ four majors, following a 6-7 6-4 7-5 6-3 victory over Djokovic on the Arthur Ashe Stadium.

Wawrinka has often been exiled from the game’s so called ‘big four’, which includes Djokovic, Federer, Rafael Nadal and Andy Murray, however it’s performances like this which makes one wonder why he hasn’t reached more finals at this level.

On the big stage Wawrinka’s record is exceptional- three major finals, three Grand Slam titles.

His performance here, with his pounding groundstrokes and bludgeoning power, stretched Djokovic to breaking point and by the fourth set the world number one required two medical time outs for an injury on his toe- which wasn’t his only issue.

The Serb was visibly in pain and when the camera zoomed in, the gushing of blood didn’t make pleasant viewing. He also appeared to be cramping and struggled to push up on his serve.

After a difficult summer, in which the Serbian lost early at Wimbledon and the Olympics, there will be questions about whether his preparations and fitness levels were at their immaculate best.

Djokovic was also in an unprecedented situation, after three of his opponents on route to the final had retired due to injury. A lack of matches may have played a factor, though nothing should detract from Wawrinka’s achievement.

Djokovic edges the opener

The world number one was striking the ball with guile and purpose in the opening set, spinning the ball high to Wawrinka’s backhand, which was nullified early on.

Serving first, Djokovic claimed an early break and quickly assembled a 5-2 lead at the start of the match.

The Serb appeared keen to stamp his authority on proceedings early on, following his loss to Wawrinka in their last Grand Slam meeting - the French Open final last year.

In the opening exchanges Djokovic’s length and accuracy from the back of the court was unmatched by the Swiss. Even so, after saving two set points on his serve, Wawrinka abruptly broke back before forcing a first set tie break.

Djokovic regrouped and refocused, claiming the breaker by seven points to one, as Wawrinka’s first serve deserted him.

In the same situation many players would have perished against Djokovic, however Wawrinka’s two victories over the Serb at Grand Slam events have both come from a set behind.

Stan comes stroming back

The trend continued here. Wawrinka broke Djokovic in the fourth game of the second set with one of his trademark backhands down the line. It was a shot which began to feature more and more as the match wore on.

Djokovic did break back but his serve began to look vulnerable and Wawrinka went on to level the match at one set all.

The Swiss stole an early lead at the start of the third, too, and by that stage he was moving Djokovic from pillar to post with his persistent power.

Djokovic, the fighter that he is, dug his heels in. He tried coming into the net and flattening out his backhand in an attempt keep Wawrinka at bay.

Injuries take their toll

The loss of the third set was a decisive blow for Djokovic, after dropping his serve at 5-6. In the semi-final against Gaël Monfils, the Serb received a medical time out for an injury on his right shoulder. Perhaps that was a reason behind his serve’s demise here.

By the fourth set the Djokovic’s body was clearly showing signs of wear, partly down TO Wawrinka; though one suspects there were other factors as well.

Djokovic called for a medical time out to treat a toe injury after falling 3-1 behind in the fourth set, much to Wawrinka’s annoyance.

The Swiss had a brief argument with the tournament director but did accept Djokovic’s apology at the sit down.

Eventually the Serb stumbled to the end of the match, as Wawrinka converted his second match point.

He had run Djokovic into the ground, something many though wasn’t even possible.