LONDON • Audacious coups by Andy Murray and Angelique Kerber have transformed the tennis landscape and they will begin 2017 eyeing the kind of domination that few would have thought possible at the start of a seismic year.
With the so-called "Big Four" in men's tennis crumbling, 29-year-old Murray emerged to seize power, winning the Wimbledon title and the Olympic gold medal before a relentless late-season charge toppled Novak Djokovic from his pedestal.
Kerber also loosened Serena Williams' grip on the women's game, reaching three Grand Slam finals and winning two of them, beginning against Williams at the Australian Open, where she became Germany's first Grand Slam winner since Steffi Graf in 1999.
Both Murray and Kerber ended 2016 as world No. 1s. Yet, back in January, Djokovic and Williams looked immovable.
Djokovic trounced Murray in three sets to win the Australian Open - emulating Roy Emerson's six titles in the process. "I feel like I've been here before," Murray quipped after a fourth defeat in a Melbourne final by Djokovic.
BRIMMING WITH CONFIDENCE
I love the conditions there and I enjoy the tournament a lot, and I'll be going in hopefully playing well and with a lot of confidence because of the way I finished 2016, so I'll give it a good go this year.
ANDY MURRAY , on his target for next month's Australian Open
Djokovic downed Murray again to win the French Open in June, taking his haul of Grand Slams to 12, meaning he held all of the sport's crown jewels simultaneously.
What is more, with Roger Federer and Rafael Nadal nursing injuries and Murray seemingly under his spell, Djokovic's path to the first calendar-year Grand Slam since Rod Laver in 1969 looked inviting.
But the wheels fell off at Wimbledon. Big-serving American Sam Querrey ambushed Djokovic in the third round - snapping the Serb's run of 30 straight wins in Slams.
It opened the door for Murray and, when Milos Raonic outlasted Federer in the semi-final, it meant the Briton would start his ninth Grand Slam final as favourite.
Raonic, the first Canadian man to reach a Grand Slam final, brought his huge power game to Centre Court but Murray shrugged him off with a classy straight sets victory.
Afterwards Murray spoke of his aim to dethrone Djokovic in the rankings - something that seemed nigh on impossible when he trailed by 8,000 points in March.
After becoming the first player to win consecutive Olympic titles, edging out a revitalised and fit-again Juan Martin del Potro in the Rio final, Murray's tank looked empty.
NOT JUST A GREAT DEFENSIVE PLAYER
She doesn't just play defence anymore. She plays aggressively. Her forehand down the line is one of the best in the game. She threads the needle beautifully.
MARY JOE FERNANDEZ , United States Fed Cup captain, on how much Angelique Kerber has improved her game to become the world's top woman tennis player.
A weary defeat by Japan's Kei Nishikori followed in the US Open quarter-finals and Djokovic, who wept after losing to del Potro in the first round of the Olympics, seemed to have recovered his mojo.
But the Serb ran into an inspired Stan Wawrinka in a raucous final that saw the Swiss repeat the savagery he inflicted on Djokovic to win the 2015 French Open.
Murray, back in harness with coach Ivan Lendl, steamed through the rest of the year, reeling in Djokovic with titles in Beijing, Shanghai, Vienna and Paris before crowning his No. 1 status by thrashing the Serb to win the ATP World Tour Finals.
If the Scot stays fit and enthusiastic, he is perfectly placed to add to his three Grand Slams, given Djokovic's vulnerability and the gap to the next tier of contenders.
Roger Federer, at 35 and out of the game with knee and back problems since July, and 30-year-old Rafael Nadal, cut down by a wrist injury at Roland Garros that forced him to miss Wimbledon, have a lot of work to do to re-establish themselves as consistent frontline challengers.
The odds are against them. They have taken substantial ranking hits, Federer out of the top 10 for the first time in 14 years, down at 16, and Nadal slipping to ninth.
Of the new intake at the top, Dominic Thiem, 23, did not show his best at the ATP World Tour Finals but will surely make an impact soon, as will the ever-volatile Nick Kyrgios, 21, the increasingly impressive Raonic, 26, and the winner of three Grand Slams Wawrinka, 31, whose power and strength invariably illuminate the big tournaments but who admitted last month that he is slowing down.
Only Djokovic, 29, is a realistic challenger to Murray's No. 1 ranking but there is a definite sense his iron will is not what it was - although he is still an extraordinary player and will probably close the two-title gap on Nadal's 14 Majors.
Murray begins his reign in earnest after only the briefest rest, at the Australian Open in Melbourne, from Jan 16. For the first time, he will start as the favourite.
"I've played really well there in the past and it hasn't happened for me, so I'll need to do something a little bit different this year," he said.
"I love the conditions there and I enjoy the tournament a lot, and I'll be going in hopefully playing well and with a lot of confidence because of the way I finished 2016, so I'll give it a good go this year."
Kerber burst from the pack chasing Williams to stun the American in a thrilling Australian Open final, depriving the 35-year-old of the 22nd Grand Slam that would have tied her with Graf.
Williams fell short again when she lost to Spain's Garbine Muguruza, 23, in the French Open final but finally matched Graf when she beat Kerber to win a seventh Wimbledon crown.
Her hopes of a record 23rd were dashed at the US Open where she suffered a semi-final defeat by Karolina Pliskova, 24. That defeat sealed Kerber's rise to No. 1 in the rankings and the 28-year-old rubber-stamped her status with victory over Czech Pliskova in the final.
It all adds up to a phenomenal season and further proof that it is possible to make a breakthrough at an advanced tennis age.
Always a great defender and counter-puncher with a capacity to hit the crowd-pleasing shot, Kerber has made her big move by getting fitter and even quicker, by attacking with more frequency and by making subtle improvements to her still vulnerable serve.
Said Mary Joe Fernandez, the United States Fed Cup captain: "She doesn't just play defence anymore. She plays aggressively. Her forehand down the line is one of the best in the game. She threads the needle beautifully."
As thoughts turn to a new season, the sport's organisers can only hope to be spared the controversies that blighted 2016 in the form of match-rigging allegations and Maria Sharapova's doping suspension.
The Russian superstar's ban for testing positive for Meldonium will end in April to add another fascinating plot line.
REUTERS, THE GUARDIAN, NEW YORK TIMES