By Martyn Herman
LONDON (Reuters) - A year in which a British man won Wimbledon, Roger Federer's star began to fade and doping reared its ugly head was defined by the dominance of two players - Rafa Nadal and Serena Williams.
Between them they won half of the grand slam singles titles on offer, triumphed at 21 tournaments in total, collected more than 150 match wins and $25 million in prizemoney.
Not bad considering both have battled back from potentially career-ending injuries.
Written off by some when his knee problems returned with a vengeance in June 2012, Nadal launched a comeback in Chile in February that was nothing short of extraordinary.
Playing like a man on a mission Nadal won 10 titles, including the French Open and U.S. Open, and reclaimed the world No.1 ranking for the first time in more than two years.
The Mallorcan was expected to dominate again on clay, which he did, culminating in an eighth Roland Garros title when he beat countryman David Ferrer. But he reached new heights on the hard courts that had proved his Achilles heel.
After beating arch-rival Novak Djokovic on his way to the Rogers Cup in Toronto, Nadal claimed the Cincinnati crown before taking New York by storm, winning the U.S. Open for the second time with victory over Djokovic.
The only blip in a season of 75 match wins and 14 finals from 17 tournaments was at a wildly unpredictable Wimbledon where he lost in round one to Belgium's Steve Darcis.
Nadal's defeat came in a first week that included Wipeout Wednesday, when seven-times champion Federer was spanked by 116th-ranked Ukrainian Sergiy Stakhovsky and a host of top names pulled up lame, some blaming dangerous court conditions.
Through the carnage Murray rode like a knight in shining armor to finally deliver the men's title for success-starved British fans after 77 years of waiting.
The Scot, reduced to tears by Federer the previous year after losing in the final, coped with the suffocating weight of expectation to beat Djokovic in straight sets on a sun-kissed Centre Court.
Djokovic did not do much wrong in 2013, beginning the year with a third consecutive Australian Open title and ending it on a 24-match winning streak including victory over Nadal in the ATP World Tour Finals.
It was the perfect response to Nadal snatching back the world No.1 ranking in October and keeping it into 2014.
"We make each other better players. We make each other work harder on our games, especially when we play against each other. It's always a huge challenge," Djokovic said of a rivalry that looks set to continue into 2014 and beyond.
With Murray having undergone back surgery and a fading Federer down at world No.6 having managed a solitary title, cracks are appearing in the so-called "Big Four" and Juan Martin del Potro and Tomas Berdych will be sensing some grand slam opportunities next year.
As for the next generation, Poland's Jerzy Janowicz, who scared Murray in the Wimbledon semi-finals, Bulgarian Grigor Dmitrov and Canada's Milos Raonic will hope to make a move.
The women's game is sadly lacking the same edge as Serena Williams appears to be playing tennis from a different planet.
Despite being the wrong side of 30 the American finished the year zooming away from her rivals and, providing she stays fit, it is hard to see who can halt her march towards Steffi Graf's record 22 grand slam titles over the next couple of years.
She took 11 titles, won 78 matches and suffered only four defeats, claiming a record $12 million in prize money.
Winning the French Open and U.S. Open took her grand slam singles haul to 17, just one behind fellow Americans Chris Evert and Martina Navratilova.
The bad news for the chasers such as Belarussian Victoria Azarenka, who took advantage of Serena's early Australian Open exit to retain her title, China's Li Na and Russian Maria Sharapova is that Serena still wants to improve.
"I have some areas where I can do a lot better for next year and I look forward to it," said the oldest women's world No.1.
"There's definitely a lot of things I can add to my game, a multitude of things. Overall I'll remember the wins, but I also want to learn from my mistakes so I don't repeat them."
Williams lost in the Wimbledon fourth round to Sabine Lisicki who went on to reach the final where she froze against unorthodox Frenchwoman Marion Bartoli. Weeks after winning her first grand slam title Bartoli retired from the sport.
In team tennis the Czech Republic retained the Davis Cup, beating Serbia in Belgrade while Italy won the women's Fed Cup.
With the International Tennis Federation tightening its anti-doping controls after concerns from the likes of Federer and Murray, two high-profile players fell foul of the system.
Croatia's Marin Cilic served half of a nine-month ban for testing positive for a banned stimulant while Serbia's Viktor Troicki is serving a 12-month ban for failing to give a blood sample at the Monte Carlo Masters.
When Djokovic won the Tour Finals in London he raised the newly-named Brad Drewett Trophy above his head - a fitting tribute to ATP president Brad Drewett who died this year.
(Reporting by Martyn Herman; editing by Robert Woodward)