World No. 1 Rafael Nadal believes Roger Federer is avoiding playing on clay to maintain his winning aura.

The clay-court season is in full swing and Nadal is dominating as expected, having recently won his second title in the Barcelona Open last weekend following his Monte-Carlo Masters win last month.

The Spaniard will play in the Madrid Open next which takes place from May 7-13 and will need to retain his title there as well as the French Open if he wants to remain above Federer in the rankings, while he can also extend his slight 100-point lead if he progresses further than the quarterfinals in the Rome Masters.

However, Federer is a key absentee during the clay swing yet again as he decided to skip it for the second year running as Nadal was hopeful of playing the Swiss legend in Madrid where he is the hometown favorite.

"With Federer I played a few times here [in Madrid]. In 2009, 2010 and 2011," Nadal said, as per the Express. "The matches against him are always difficult, but in Madrid a little more. They have been special meetings, and having been able to live them at home is something unique."

Nadal previously joked that Federer was avoiding him on clay but understands why at 36 years of age, he is deciding to avoid the surface that has resulted in minimum success for him, at least compared to other surfaces.

However, Nadal also believes Federer, who has a 13-2 losing record against him on clay, will lose his winning aura if he takes part in the clay events, especially considering the 20-time Grand Slam winner has suffered just seven losses since the start of 2017.

"I understand that Federer must think that it is a major wear to play on the [clay] ground, that he has a fantastic winning dynamic and that in clay he can lose more games and lose that aura of unbeatable that he maintains on other surfaces," Nadal added. "I think those two factors together lead him to make the decision. It is respectable, and while it works… In 2017 it was perfect, what will it change?"

Meanwhile, Federer added to Nadal's points as he explained why he made his choice to skip the clay-court season for the first time since making the announcement after the Miami Open in March.

"I am not 25 any more I need to reserve some energy for Wimbledon," Federer said, as per Tennis World USA. "I love the grass more than the clay court, so that is why I won’t take part this year."

Federer recently updated his tournament schedule and will return for the grass events that begin in June. Interestingly, there was no initial mention of the Mercedes Cup in Stuttgart but he announced Wednesday on his Facebook page he would be taking part.

He will then take part in the Halle Open in Germany before embarking on a potential ninth Wimbledon crown as he looks for a second Grand Slam title of the year.