The new tennis season kicks off with doubts over big names and opportunities for others as the Australian Open rolls around again.
Andy Murray, Serena Williams and Kei Nishikori have all pulled out of the year's first grand slam, which begins on January 15.
Here are the 10 names likely to challenge for the titles or spring a few surprises.
While his younger rivals battle their bodies, Federer sails serenely on. Twelve months on from his remarkable 18th grand slam title, the 36-year-old heads to Melbourne as the favourite to become the first man to reach 20 singles crowns. As long as his sometimes suspect back holds up, there is nothing to suggest Federer will be in anything less than top shape at a tournament he has won five times.
The absence of defending champion Serena Williams opens the door for a new champion, and world number one Halep must sense a big opportunity. The Romanian fell agonisingly short of a first grand slam title in 2017 but was the most consistent of the top players. Although at her best on clay, Halep is well capable of winning the biggest tournaments on hard courts. The 26-year-old is a two-time quarter-finalist in Melbourne but has not won a match since 2015.
Last season gave renewed hope that Dimitrov might still blossom into the grand slam champion he seemed set to become as an extravagantly-talented junior. The Bulgarian came agonisingly close to beating Rafael Nadal in the semi-finals in Melbourne and finished the season ranked third after winning the biggest title of his career at the ATP Finals in London.
After lifting the biggest title of her career at the WTA Finals in Singapore to finish 2017, Wozniacki heads into the new season full of confidence and hot on the heels of Halep. The Dane has been touted as a potential grand slam winner for nearly a decade but is still only 27 and showed a new-found aggressive approach in her game last season that should make her a big threat to all.
Juan Martin del Potro
Del Potro has not played in Melbourne for four years because of his injury troubles but heads back with his status as a grand slam contender restored by his memorable run to the US Open semi-finals. Battling illness, the Argentinian came back from the dead against Dominic Thiem before shocking Federer and went on to finish the season very strongly.
The big-hitting German has always had the potential to achieve great things yet it was only last season that she managed to find the consistency needed to challenge at the top. Now 29, she finished 2017 by winning back-to-back titles in Moscow and Zhuhai and extended her winning run to 14 matches by defeating Wozniacki to open the season with a trophy in Auckland. Now ranked 12th but still under the radar.
The 20-year-old Russian is not the most high profile of the 'Next Gen' stars emerging but became the first to reach a grand slam quarter-final thanks to a superb run in New York. Still something of a raw talent, Rublev expends too much emotional energy on court but the brilliance of his ball-striking, particularly on the forehand side, is without question.
Barty goes into the Australian Open as the highest-ranked home female player after a phenomenal 2017. Diminutive yet powerful with great variety in her game and a tremendous tennis brain, the 21-year-old has already had a roller-coaster career. A junior prodigy, she stepped away from the game in 2014 and tried her hand at professional cricket before returning to tennis in 2016.
Like Dimitrov, an artist rather than a power merchant, 2017 was the year that saw Goffin take his place at the top table. The Belgian lost nearly two months after suffering a hugely unfortunate ankle injury at the French Open yet still qualified for the ATP Finals and stunned Federer before losing to Dimitrov in the final.