At the start of the year the long reign of the ''Big Four’’ seemed to be in some danger. The dominance of Roger Federer, Rafael Nadal, Novak Djokovic and Andy Murray was not as clear cut as in the past.

Not only was age catching up with them a whole set of young challengers notably Marin Cilic of Croatia, Alexander Zverev of Germany, Juan Martin del Potro of Argentina, Grigor Dimitrov of Bulgaria and Dominic Thiem of Austria had made rapid progress and it appeared that a new order would take over from the old guard.

After all two of them had won a Grand Slam with Cilic coming up trumps at the US Open in 2014 and del Potro winning the same event five years earlier. Cilic was also finalist at Wimbledon last year while del Potro was a semifinalist in 2013.

And yet as we come to the last Grand Slam of the year the US Open which gets underway on Monday the old guard has made it clear that they are not yet ready to ride off quietly into the sunset. The three Grand Slams have been won by Federer, Nadal and Djokovic, Nadal and Federer still occupy the first two places in the ATP rankings while the Serb is No 6, Nadal and Federer are top seeded for the US Open while Djokovic Is the No 6 seed. In addition just last week Djokovic became the first player ever to win all nine Masters 1000 events since the series started in 1990.

The recent form of Djokovic a two time winner at the US Open has made him an early favourite for the title despite the presence of all the leading players. And this signals a remarkable transformation in his fortunes as for much of the earlypart of the year the Serb’s form was indifferent. An elbow surgery had kept him out of action for quite a while and predictably enough when he came back shortly after the season started his form was patchy. He had bad defeats in early rounds and this saw him slide down the rankings to 21.

He came into his own shortly before Wimbledon commenced by finishing runner-up at Queen’s club but even then hardly anyone looked upon him as a serious contender. He was seeded 12th and with the fierce competition available in the men’s event everyone was looking to either Federer or Nadal, the top two ranked players to take the title. Or it was reckoned that perhaps one of the quintet of young challengers were in with a chance.

And yet it was Djokovic who lifted the trophy getting the better of Nadal in a classic semifinal and then quelling the challenge from the fast rising South African Kevin Anderson in the title clash. Since then he has maintained his form climaxing in the Cincinatti Masters with a straight sets victory over Federer who was eliminated in the quarterfinals at Wimbledon by Anderson.

Interestingly Djokovic leads the pair’s all-time series 24-22 and he has dominated the biggest matches. He is 3-1 against Federer in Grand Slam finals and 12-6 overall in championship matches, including wins at Wimbledon and the US Open in 2015.

So now the reconstituted''Big Three’’ will be up for the challenge from the younger brigade in the US Open. Murray has missed most of the season following a hip surgery. He was a last minute withdrawal from Wimbledon and though he did play a few tournaments he clearly was well below his best and at present has slid to 378 in the rankings. He is participating in the US Open but whether he can come back from his serious injury and subsequent steep fall in the rankings must be in doubt.

However Federer, Nadal and Djokovic are still in the running for the top titles and this says a lot for their skill, stamina and staying power. So will the dominance of the Big Three continue? Or will one of the younger challengers emerge as champion? The battle for supremacy in the intensely competitive world of men’s tennis promises to make the US Open a tournament to be followed keenly.

As far as the women’s event is concerned it is even more open and unpredictable. Any one of the top ten ranked players has an almost equal chance but interest will again centre round Serena Williams, seeded 17th. Against all odds she made it to the final at Wimbledon before going down to Angelique Kerber so one can never rule out her chances of winning the trophy and notching up her long awaited record equaling 24th Grand Slam title. However even in an open field the front runners will still be world no 1 Simona Halep, Kerber and defending champion Sloane Stephens.