Rafael Nadal
Rafael Nadal is keen to move ahead in the quest for his ninth title in Barcelona. Reuters

Rafael Nadal's struggle on clay has been a big story in the tennis world as of late. For the first time in his career, the impregnable Mallorcan Bulls has apparently turned into a mortal after failing to make the finals of two high-profile clay court tournaments.

Nadal, who is gunning for a record ninth French Open title next month, is surprisingly playing below expectations this past few weeks. His quarterfinals losses against Nicolas Almagro (Barcelona Open) and David Ferrer (Monte Carlo Masters) have certainly casted a dark cloud on his ability to stay dominant in his most favorite court surfaces.

Moreover, the 27-year old Spaniard admitted that he's currently experiencing a drop in confidence level, just a year after racking up 10 titles - including two Grand Slam championships (US and French Open crowns).

"I started the season okay except for some lack of confidence and competitiveness in important moments of certain matches," Nadal told ESPN days before the Barcelona Open.

"I've faced adversities throughout my career, and this is just another one. All my rivals are dangerous. Every one of them, I always go out there to play knowing that I can win or lose."

There's also a concern about his capacity to defend his status as the top netter in the world. According to Carl Bialik of Five Thirty Eight, Nadal had already suffered back-to-back setbacks on clay twice before and he responded with a long clay-winning streak in both occasions.

However, with the emergence of Djokovic and Stanislas Wawrinka, Nadal is perhaps in for the most challenging clay-court season in his career.

"Twice in his nine-year run of dominance, Nadal lost on clay in consecutive tournaments: in 2009, to [Robin] Soderling and [Roger] Federer; and in 2011, twice to [Novak] Djokovic. Immediately after each pair of losses, Nadal went on big clay-winning streaks: 37 straight matches after his 2009 rut, and 22 straight starting in 2011," Bialik stated in his article.

"He may need another such run to maintain his No. 1 ranking: His lead over Djokovic is fewer than 2,000 points, and Nadal has 4,000 points to defend in his next three tournaments. Djokovic has just 910 points to defend during that span."

Nadal is scheduled to play in the upcoming Matua Madrid Open, where he is three-time champion.