At the year's beginning 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. The gap in the rankings was narrowing and it appeared that a new order might just take over from the old guard.

Yet as we come to the end of the season tournaments with the conclusion of the US Open, the last Grand Slam of the year, the old guard has made it clear that they are not yet ready to ride off into the sunset. For a start the four Grand Slam events were all won by three of the quartet, with Federer winning the Australian Open, Nadal as usual reigning king at Roland Garros, and Djokovic emerging triumphant at both Wimbledon and the US Open. Nadal, Federer and Djokovic occupy the first three places in the ATP rankings. The one major casualty has been Murray who missed most of the season because of injury, which in turn led to early losses in the few tournaments he played, sliding sharply to 307 in the rankings.

Indeed it is quite remarkable that the trio of Federer, Nadal and Djokovic have won 47 out of 55 Grand Slam events beginning with the French Open in 2005. Wimbledon of course has been dominated by the quartet with every title since 2003 being their monopoly. And while it is a tribute to Federer and Nadal that after all these years they still remain on top, the true success story of the year’s tennis season has been Djokovic, not just because he won two Grand Slams in a row in addition to becoming the first player ever to win all nine Masters 1000 events since the series began in 1990.

It is Djokovic's comeback story that makes for inspirational reading. For much of the early part 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 began his form was patchy. He had bad defeats in early rounds and this saw him slide down the rankings to 21.

Never one to give up easily, Djokovic took steps to change his fortunes and begin a resurgence. He changed rackets, tweaked his serve a bit, began working with a new team and even took up meditation in the hope of remaining calmer on the court, this involving a five day trek up the French Alps.

All this seemed to have a positive effect for he came into his own shortly before Wimbledon commenced, finishing runner-up at Queen’s Club, but even then hardly anyone looked upon him as a serious contender for the Holy Grail of tennis. He was seeded 12th and with the fierce competition on hand in the men’s event everyone was looking to either Federer or Nadal, the two top ranked players, to take the title. Or it was reckoned that perhaps one of the quintet of young challengers was in with a chance.

And yet when it was all over 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.

Djokovic then maintained his form, winning the Cincinnati Masters with a straight sets victory over Federer. And then of course came about the climax of his comeback with the title win at the US Open, defeating Del Potro in straight sets in the final. The win put him level with Pete Sampras with 14 Grand Slam singles titles, with only the 'Big Two' of Federer (20) and Nadal (17) ahead of him. This has given rise to increasing speculation whether Djokovic can catch up with Federer and Nadal, particularly since he is the youngest of the trio, still fit and agile and playing as well as ever. 2019 could well provide the answer to that . . .

But 2019 might also answer whether the ever growing band of young players have it in them to take over from the reconstituted 'Big Three', as it is unlikely that Murray will climb back enough to be taken as a serious contender for the majors. That they continue to be in with more than a chance is underlined by the fact that Cilic was runner up at the Australian Open, Thiem was runner up at the French Open, Anderson the runner up at Wimbledon and Del Potro the runner up at the US Open. Nor can one write off Dimitrov and Zverev despite a fairly indifferent 2018 for both players.

And who knows? The year may throw up some surprise packages. Anderson for example was nowhere near the top at the start of the year. He is now ranked No 9, and his performance at Wimbledon has made him a well known figure around the tennis world and a respected player around the circuit. Another exciting talent to watch for is 20-year-old Stefano Tsitsipas of Greece who has rocketed from nowhere to No 15 in the current rankings.

So once again 2019 should see an engrossing duel for supremacy between the Big Three and the young challengers. So far the old guard has been holding firm. It remains to be seen whether there will be a change in the script next year.