Rafael Nadal
Nadal (R) is the world number one at the moment with Federer in second. In this picture, Federer of Switzerland and Nadal of Spain pose with their trophies after the Men's singles final mach on day eight of 2017 ATP Shanghai Rolex Masters at Qizhong Stadium in Shanghai, China, Oct. 15, 2017. Lintao Zhang/Getty Images

Roger Federer and Rafael Nadal’s battle for the top spot in the ATP men’s singles ranking is set to continue as the Spaniard begins his title defense at the Monte Carlo Masters.

The Swiss ace took over at the top of the rankings in February from Nadal after he won the Rotterdam Open. He became the oldest world number one in ATP history.

But Federer’s reign at the top was short lived after he failed to defend his titles at the Indian Wells and Miami Masters Series events in March. And despite not playing a single ATP event this year, Nadal was back on top of the rankings for the start of the clay court swing of the season.

The 31-year-old is top of the standings, but is just 100 points ahead of his long-time rival, who has chosen to skip the entire clay court swing of the season including the French Open. Federer will not be losing any points as he did the same in 2017 putting all the pressure on Nadal.

Nadal has 4,680 points to defend over the next one and a half months after winning titles at Monte Carlo, Barcelona, Madrid and Paris in 2017. Again, similar to the Spaniard, Federer can return to the top of the rankings without playing even one event on clay.

Nadal has to win the title in Monte Carlo to remain the world number one as even a loss in the final will see him lose 400 points, which will put him behind Federer in the rankings. The 16-time Grand Slam winner next plays in Barcelona and Madrid where he won titles in 2017, which means he cannot make up any points.

The only opportunity for Nadal to make up points on clay this season is at the Italian Open owing to his loss in the quarterfinals in 2017. Apart from that, he has maximum points to defend in all the tournaments he plays on clay this season.

The ten-time French Open champion is favorite to dominate this part of the season yet again, but he will be under added pressure in order to maintain his place as the world number one until the end of the clay court season which concludes June 10 with the culmination of the second Grand Slam of the year at Roland Garros.

Federer next returns to the court at the Gerry Weber Open in Halle, Germany in June – a tournament he uses to help prepare him for the Wimbledon Championships in July. The Swiss maestro is targeting an unprecedented ninth title at SW19 after winning his eighth last season.

If the ranking switches during the clay season, it will again come into play during the grass court season later in the year where Federer will be defending titles in Halle and London. This could continue until the end of the year, with no other player close enough to challenge the veteran duo at the moment.