The 2017 season reached its final milestone as the Nitto ATP Finals landed in Grigor Dimitrov's lap last Sunday at the O2 Arena in London. However, the main storyline of this season has been Roger Federer and Rafael Nadal, iconic veterans of the sport that decided to give it another go this year. Back in January, they both entered a new chapter of their rivalry with Federer skidding past Nadal in that epic final at Melbourne Park. At the time, most people considered the match as a one-hit wonder, a farewell gift, or something similar. Two months later Federer was still on fire winning back-to-back titles at Indian Wells and Miami.

Rafael Nadal remains a great threat for Federer

Basically, where Federer was absent it was Rafael Nadal who stepped in to steal the show and the exceptions were rare. Although a new wave of ATP tennis stars has been moving up in the rankings, the old guard is still in place. And for Federer, those ancient shadows are likely to pose the biggest threat in 2018. Rafael Nadal ended the year at No. 1 the world and he will seek to enforce his dominance next year. The Spaniard seemed a bit deflated towards the end of the year but that's mainly due to his excruciating schedule of 2017. He ends the year with 78 matches under his belt holding an impressive 67-11 win/ loss record.

Despite losing all the last five matches he played against Roger Federer, Rafael Nadal is expected to step up his game too.

After all, he used to be the genuine representation of Federer's worst nightmare in terms of head to head stats. Nadal won most of his biggest battles on clay but he has a great history on other surfaces too. You just need to remember those two epic Grand Slam finals (2008 Wimbledon and 2009 Australian Open) when Nadal conquered Federer.

All this recent history of losing over Federer did nothing but scale things up a bit. Overall, Nadal is still 23-15 in the head to head stats against Federer.

Novak Djokovic will want his crown back

A former holder of the #1 spot, Novak Djokovic, is currently ranked 12th in the world and is expected to regain that mind-blowing pace of his in 2018.

A twelve-time Grand Slam winner, the Serb tennis superstar hasn't played an official match since 2017 Wimbledon. An elbow injury and a lack of inspiration coerced him to call it a season several months earlier.

In recent years, Djokovic stood as the one who prevented Federer from winning another Grand Slam title. Outside of the top ten for the first time since his ascent to the ATP elite, the 30-year-old would love to bring those golden days back on his side. Doing an excellent job against the Swiss player, Djokovic dominated Federer from the baseline perhaps even better than Nadal did in his prime years. Overall Djokovic leads Federer by 23-22.