Rarely has there been such intrigue at the start of a new tennis season after Andy Murray and Angelique Kerber created a new order by toppling Novak Djokovic and Serena Williams.
It was a case of expected the unexpected in an eventful 2016 that saw Kerber and Murray take over at the top of the world rankings for the first time.
While Djokovic and Williams lost their way, Murray and Kerber went from strength to strength and must have been wishing the year would never end.
There was also the shock of Maria Sharapova's ban for a failed drugs test, while legendary duo Roger Federer and Rafael Nadal suffered injury problems in a season that produced high-profile coaching changes.
With plots aplenty to keep an eye on over the next 12 months, here we look at some the issues to look out for in 2017.
WILL DJOK TAKE STOCK AND COME BACK STRONGER?
When Djokovic completed a career Grand Slam by claiming an elusive maiden French Open title in June, the Serb held all four major titles.
The usually unflappable Serb was brought down to earth with a bang when he was sensationally beaten by Sam Querrey in the third round at Wimbledon and spoke of "private issues" that he was struggling with following his exit on the famous grass at SW19.
Djokovic also lost to Juan Martin del Potro in the first round of the singles at the Rio Olympics and took a break before losing to Stan Wawrinka in the US Open final.
The 29-year-old looked in need of another rest when Murray beat him in the ATP World Tour Finals to end his long reign as world number one and has since parted company with coach Boris Becker.
Murray was in a class of his own at the back end of a year in which he was reunited with coach Ivan Lendl, but Djokovic will be a man with a point to prove next season with a new coach in his corner.
CAN SERENA MATCH KERB'S ENTHUSIASM
Williams spent an incredible 186 weeks at the top of rankings before losing that status with a defeat to Karolina Pliskova in the semi-final of the US Open.
While the legendary American was able to equal Steffi Graf's Open Era record of 22 major titles by winning at Wimbledon, that was the only grand slam crown she was able to claim this year.
Kerber set the tone by landing her first major at the Australian Open and the German went on to claim another at Flushing Meadows after losing to Williams in her maiden final at the All England Club.
Powerful left-hander Kerber also won the WTA Finals as she thrived on usurping Williams and took silver in the women's Olympic singles, so the 28-year-old has a lot to live up to this season.
Williams insists she is not finished yet, though, and after her engagement to Alexis Ohanian was announced she will be hoping there are more record-breaking exploits to come as well as wedding bells.
IS THE BIG FOUR NO MORE?
The so-called Big Four of Murray, Djokovic, Nadal and Federer have set the standards in men's tennis for a number of years, but that era could well be over.
Federer has dropped to 16th in the world following a spell on the sidelines with a knee injury, while Nadal - also troubled by injury problems - will start the new year ranked ninth.
While Swiss great Federer said he will be around for another two to three years, he has not won a major title since 2012 and it remains to be seen how much of an impact he can have at the age of 35 after undergoing surgery.
Nadal showed signs last season that he can still be a force, but a wrist problem hampered the Spaniard and he was forced to cut short his 2016 as the issue would not go away.
Even if they do get back to anything like the peak of their powers, the likes of Milos Raonic, Stan Wawrinka and Kei Nishikori would be entitled to question whether the Big Four is no more.
SHARAPOVA TO MAKE UP FOR LOST TIME?
A sombre Sharapova stunned the sporting world when she revealed testing positive for banned substance meldonium during the Australian Open.
The five-time major champion had a two-year ban reduced to 15 months by the Court of Arbitration for Sport after lodging an appeal.
Sharapova will be clear to return to action in April, but could take a while to get back to anything like her best after such a long spell out of the game.
The 29-year-old said she was "counting the days" until her comeback and it will be interesting to see what sort of reception the Russian gets.
RISING STARS TO SPARKLE?
Dominic Thiem and Madison Keys were among the highly regarded players to make strides in 2016, but Nick Kyrgios did not do himself any favours.
Thiem won four titles and finished the year eighth in the rankings, a position that the ever improving Keys also occupied after showing what she is capable of.
Kyrgios was banned for eight weeks for his antics during a defeat to Mischa Zverev at the Shanghai Masters and the all too often petulant Australian will need to let his tennis do the talking in order to realise his undoubted potential.
Swiss teenager Belinda Bencic is another young player with the ability to take her game to another level in 2017 and Russian Karen Khachanov is also one to watch.