Roger Federer may be breathing down his neck, but Rafael Nadal should be proud of his achievement of returning to world No 1

It may last only three weeks, but the Spaniard's success, after looking a spent force in 2015, is an impressive feat for the 15-time major winner.

Rafael Nadal will return to the top of the ATP rankings for the first time since 2014 on Monday. John Minchillo / AP Photo

There had been a number of low points on court for Rafael Nadal in recent years.

Between 2012 and 2015 he lost every year at Wimbledon to someone ranked No 100 or lower at a tournament he had won twice in the past.

But arguably the moment that summed up things best was at Roland Garros, scene of so much of the Spaniard's greatest achievements, in June 2015.

He had only ever lost there once previously, having won nine French Open titles, so to see him swept aside so comprehensively by Novak Djokovic in their quarter-final clash 7-5, 6-3, 6-1 was at times difficult to watch.

Read more by Graham Caygill

To put it bluntly, Nadal as a major winner looked done. Injuries were weighing him down, he could no longer rely on his powerful backhand dictating points from the back of the court the way he had in his youth, and his spirit appeared broken.

There was none of the fight that had been the hallmark of his career as he simply had little response to Djokovic on a surface that he previously been all but unbeatable on.

Losing so emphatically to a man who had overtaken him as the world's best must have been difficult to take, and at the time it appeared Nadal had no answer.

Yet, fast forward two years and for the first time since June 2014, Nadal will on Monday be the men's world No 1 tennis player when the ATP rankings to complete a remarkable fightback.

It is not really a time of celebration for the 31 year old, with his mind on the tragic events in Barcelona on Friday, while also preparing for his challenge to win the US Open for a third time.

But the achievement, given how much of a spent force he looked, should be highlighted, even if, with Roger Federer breathing down his neck, it might be a short tenure back at the top.

The catalyst for the renaissance was calling it quits on 2016 early in October to allow himself time to recover from a wrist injury, which had dogged his season and forced him to withdraw from the French Open and miss Wimbledon.

The time away from the court rehabilitating as well as working on his game with his coach and uncle, Toni Nadal, had the desired consequence.

It was in Abu Dhabi at the end of last year that the first signs that Nadal had re-found his step were first noticeable.

Yes, the Mubadala World Tennis Championship is an exhibition, but the way in which he took apart Milos Raonic in the semi-finals, on his way to taking the title for a fourth time was impressive.

At the Australian Open in January he demonstrated that he was a force to be reckoned with as he survived duels with Alexander Zverev, Gael Monfils, Raonic and Grigor Dimitrov, all of which went at least four sets, to reach the final where he lost in five sets to Federer.

He did not win, but Nadal, who had begun 2017 seeded ninth, had demonstrated not only had the zip in his backhand returned, but he had the stamina and fight to go toe-to-toe with younger rivals, and come out on top.

But it was on clay, the surface where he made he name, that his charge back to No 1 gained speed.

He played 25 games on clay between April and June, losing only one match to Dominic Thiem in Rome, as he dominated as he had done in his early peak years.

He dropped only 35 games in winning the French Open, a tournament he had lost so meekly at two years earlier, and the ruthless manner in which he thrashed Stan Wawrinka in an one-sided final highlighted how far he had come from looking like someone whose best days were long gone.

It has been a little anti-climactic since then. He went out in the fourth round at Wimbledon to Gilles Muller, though the fact he went out to the world No 26 was progress given he was at least in the top 100.

The absence of Andy Murray and Federer with injuries in Cincinnati over the past week meant Nadal knew, thanks to the vagaries of the ATP ranking system, that he would be guaranteed top spot seven days ago.

A quarter-final exit to Nick Kyrgios was not how he would have ideally liked to celebrate his crowning moment, but it should not detract from the accomplishment.

Yes, injuries and loss of form to other players, particularly Murray and Djokovic, has helped, but the Spaniard's brilliance on clay and a strong first third of the year on hard courts where he reached three finals in five tournaments is why he is now back on top.

Is it going to last? Probably not in all honesty. He will have No 1 for at least three weeks, with the US Open beginning on August 28, but if Federer wins it for a sixth time the Swiss player will take the place to complete his own journey back to the summit of men's tennis.

Given Federer's strong form this year, having already won the Australian Open and Wimbledon, and enjoying a record of 35-3 in 2017, it is right he starts as overwhelming favourite.

Nadal has not been beyond the last 16 at Flushing Meadows since winning it for a second time in 2013, and his quarter-final exit in Cincinnati and third-round defeat in Montreal do not scream of a man in the form to win a 16th major title next month when the final takes place in New York on September 10.

But, Nadal has been written off before and has proven people wrong, and it would not be beyond the Spaniard to spring one final shock in a year of surprises.

Until then he can, when he allows himself, reflect on an enjoyable and exciting return to the top of his sport.