PARIS: Novak Djokovic's commanding victory over Roger Federer in the final of the ATP Tour Finals in London on Monday brought the curtain down on a spectacular year for men's tennis which has rarely been in more robust health.

It was a fittingly bookend triumph for the popular Serb, who got things underway in January by defeating Rafael Nadal in a pulsating Australian Open final that took almost six hours to complete - the longest title match in Grand Slam history.

Djokovic subsequently may not have reproduced the blistering form that brought him three Grand Slam titles in 2011, but runs into the finals of the French and US Opens and the semi-finals at Wimbledon deservedly saw him finish the year on top.

It was an achievement that if anything, he said, meant more to him than what he produced in the previous year given the quality of the opposition he had to face from Nadal, Federer and Andy Murray.

For the first time since 2003, before Federer took command of the sport, the four Grand Slam titles were shared out.

Djokovic beat Nadal in five sets in Australia, Nadal beat Djokovic in four sets in Paris, Federer beat Murray in four at Wimbledon and Murray edged Djokovic in five in New York.

Murray had the added satisfaction of winning Olympic gold over Federer in London and Djokovic had the last word against Federer also in London.

Former British No.1 Tim Henman said that the way Monday's match had finished had summed the year up perfectly.

“It was a very fitting match to finish what has been an unbelievable year and it was a very fitting last shot, Djokovic under pressure out wide, able to find the passing shot and get the victory,” he wrote in his BBC column.

“I think the game's stronger than it's ever been, with Djokovic maintaining his place at the top of the game after last year, when he just dominated everything and was the clear number one.

“The margins between Djokovic, Federer, Andy Murray and Rafael Nadal are so small, it comes down to just a few points when they play each other.

“I think that's the beauty of their rivalry, that they're all capable of beating each other, which was emphasised by each of them winning one of the four Slams in 2012.”Federer, who at 31 is by far the oldest of the quartet, but who looks in superb shape and capable of playing at the highest level for a few more years, agrees that the rivalries that have emerged between the Big Four are key.

“It's part of the puzzle that makes me motivated, trying to play against the likes of Novak, Andy and Rafa,” the Swiss star said.

“It's great playing against these guys because the ball does come back a few more times than against other players and you get those great rallies going.

“I love playing against the young guys as well, because to many of them I'm an idol which is kind of strange to me.

“But it's nice seeing them grow, see what the next generation comes up with.”

Federer, Djokovic and Murray all seem set to continue at the top when the new season gets underway in Australia in January, but question marks remain over the fitness of Nadal.

The Spaniard, an 11-time Grand Slam champion, has not played since a shock defeat to unseeded Czech Lukas Rosol in the second round at Wimbledon and he has yet to set a date for his return to action as he tries to ease the pain in his knees.

The only other cloud on the horizon for men's tennis appears to be that there is little new talent coming through in the 18-24 age-group - Nadal is 26 while Murray and Djokovic are 25.

Promising juniors like Bernard Tomic, Marin Cilic and Grigor Dimitrov have so far failed to contest at the topmost level, while Juan Martin del Potro, who is 24, struggles to compete consistently due to injuries.

Still, tennis can look forward to another stellar year in 2013 with Djokovic, Federer, Murray and hopefully Nadal at the helm.