© Peter Staples/ATP World Tour

Alexander Zverev soared to as high as No. 3 in the Emirates ATP Rankings in 2018.

Will New Faces Challenge Legends For No. 1 Mantle in 2018?

ATPWorldTour.com previews the 2018 season

The 2016 battle for No. 1 finished in a sprint, with Andy Murray winning 24 consecutive matches and five consecutive titles to edge Novak Djokovic. The 2017 season also featured a two-man race, as Rafael Nadal beat out Roger Federer to finish atop the Emirates ATP Rankings for the fourth time, and, at 31, become the oldest year-end No. 1.

But the 2018 battle for the top spot hardly looks as if it will be a mano-a-mano contest. Rather, next year's fight for No. 1 in the Emirates ATP Rankings looks as wide open as any in recent memory. The seven men who could finish on top:

Nadal

1) No. 1 Rafael Nadal

Nadal could very well back his 2017 and finish atop the Emirates ATP Rankings for a fifth time. Spoiler alert: The Spaniard will again likely pick up thousands of Emirates ATP Rankings points on the European red clay. He will be going for his 11th title at each of the following tournaments: Monte-Carlo, Barcelona and at Roland Garros. Not to be overlooked, though, Nadal's game on hard courts in 2017 was as good as anyone's. The Spaniard won two of his six titles on the surface, including his third US Open crown, which was his 16th Grand Slam trophy.

But can Nadal's body – namely his left wrist and his right knee – withstand another full season on the ATP World Tour? He's already pulled out of the Brisbane International presented by Suncorp because he needs more time to recuperate from his right-knee injury, which forced him to participate in but eventually withdraw from the final two tournaments of 2017 – the Rolex Paris Masters and the Nitto ATP Finals.

Federer

2) No. 2 Roger Federer

It's hard to imagine Federer, who will turn 37 in August, having a better season in 2018 than he did in 2017. To refresh: He played in 12 tournaments and won seven of them, including two Grand Slams – the Australian Open and Wimbledon – and three ATP World Tour Masters 1000 events – the BNP Paribas Open, Miami Open presented by Itau and the Shanghai Rolex Masters. Before 2017, Federer hadn't won a Grand Slam in five years – the last coming at 2012 Wimbledon – and he hadn't captured a Masters 1000 since August 2015 (Western & Southern Open in Cincinnati).

Federer's masterful managing of his 2017 schedule was one of the keys to his success – he played in only 12 tournaments, and did so after a six-month break in 2016. Before the 2018 season, however, the Swiss right-hander will have only a six-week break. How will his back and left knee hold up with such little time to recover after his 2017?

Dimitrov

3) No. 3 Grigor Dimitrov

Say what you want about Dimitrov before 2017, but the Bulgarian officially arrived as a Top 5 player this season. He won his maiden Masters 1000 title in Cincinnati and backed it up by going unbeaten in his debut at the Nitto ATP Finals to win the biggest title of his life. On paper, he is a clear contender to compete for the year-end No. 1 spot in 2018. Dimitrov finished 2017 at No. 3 in the year-end Emirates ATP Rankings, a career high.

But he's never been in this position before, having to defend so many Emirates ATP Rankings points and having to back up a Top 5 season. How will he respond? Then again, Dimitrov had never played in the season-ending finale in London before, either, and he had no trouble finishing his year on a perfect note at The O2.

Zverev

4) No. 4 Alexander Zverev

The Grand Slam fanatics will point to his record in Slams, something Zverev has been reminded of often. The 20-year-old has never made it past the fourth round of a Grand Slam, and he's reached that stage only once, at 2017 Wimbledon. But look no further than his record in finals as a potential rebuttal: In 2017, Zverev was 5-1 in title matches, and two of those wins came against two of the best players in the world.

Zverev beat Novak Djokovic to win his first Masters 1000 title at the the Internazionali BNL d'Italia in Rome, and the 6'6” German defeated Federer to win his second Masters 1000 crown at the Coupe Rogers in Montreal. Surely, as Zverev bulks up in the off-season and gains more experience in five-set matches, his success at all tournaments, including Grand Slams, will come.

Wawrinka

5) No. 9 Stan Wawrinka

Climbing to No. 1 is one of the bullet points missing from Wawrinka's Hall of Fame resume, which includes three Grand Slam titles and a Masters 1000 trophy (2014 Rolex Monte-Carlo Masters, d. Federer). Wawrinka was No. 3 before he had to end his season after an early Wimbledon exit (knee injury).

Wawrinka and coach Magnus Norman have split, but the 32-year-old Swiss still has someone else very important on his side: Pierre Paganini, the trainer he shares with Roger Federer. Paganini guided Federer during his delicate recovery and comeback in 2017, and he'll try to do the same with Wawrinka next season.

Novak 
6) No. 12 Novak Djokovic

The top Emirates ATP Ranking spot was Djokovic's home for 223 weeks, including four year-end No. 1 finishes (2011-12, 2014-15). And Djokovic was there as recently as 31 October 2016, before Murray took over the top place at the Rolex Paris Masters.

But the 30-year-old Serbian hasn't played a match since retiring against Tomas Berdych in the quarter-finals of The Championships, Wimbledon, and just how well is his right elbow, which forced him to miss the second half of the 2017 season and had bothered him for 18 months?

Do not, however, underestimate two things about Djokovic's comeback: He has had six months to rest his mind and body, a tactic that seemed to work out well for Federer, and Djokovic appears to have his team set. After splitting with long-time coach Marian Vajda in May 2017, Djokovic has brought on former World No. 1 Andre Agassi and the recently-retired Radek Stepanek.

<a href='https://www.atpworldtour.com/en/players/andy-murray/mc10/overview'>Andy Murray</a>

7) No. 16 Andy Murray

The Scot surely would have preferred a more fruitful stay at No. 1. Murray, who ascended to the top place in November 2016, fell from No. 1 in August after eight months of not playing his best tennis. In 2016, Murray finished 78-9, including his 24-match win streak to end the year. In his injury-shortened 2017, the Brit went 25-10, calling it a campaign because of his lingering hip injury after a Wimbledon quarter-final loss to American Sam Querrey.

But if Murray is healthy, why not expect the Brit to once again beat the very best in men's tennis? In 2017, neither Federer nor Nadal matched Murray's 24-match win streak, and the three-time Grand Slam champion and 14-time Masters 1000 titlist relishes facing a doubting audience.