King Rafael Nadal under pressure

The King of Roland Garros has never looked so exposed.

A trip to Paris for the year's second grand slam is usually Rafael Nadal's time to shine, and almost always add to his burgeoning trophy cabinet.

In 2015, Nadal heads to the clay courts under all sorts of pressure - and because of more than just defending his title.

Nadal is seemingly defending his aura, for the first time since 2004 entering the French Open without a European clay-court tournament win.

Usually, the Spaniard looks unbeatable - at least by anyone other than Novak Djokovic.

This time, he appears brittle and lacking confidence and consistency, with losses to Djokovic (Monte Carlo), Fabio Fognini (Barcelona), Andy Murray (Madrid) and Stan Wawrinka (Rome).

Never has a better opportunity presented itself to Djokovic to finally win an elusive French Open crown, with his runner-up finishes in 2012 and '14 the closest he has come.

Only Roger Federer (2009) was able to break Nadal's stranglehold on the tournament, with the left-hander winning nine of the past 10 editions.

Making things even more difficult for Nadal is his rankings drop, a slip to seventh sure to make his run through tougher.

Djokovic is the man to beat, but Federer, Andy Murray and perhaps even Kei Nishikori are capable of threatening.

The women's draw is just as open, even though Maria Sharapova has made the past three finals - winning two.

Underlining her credentials, Sharapova claimed the title in Rome in the lead-up.

Boosting the Russian's chances is the lack of clay-court practice for Serena Williams, the world number one who withdrew in Italy due to an elbow injury.

Williams said she pulled out to avoid causing further damage, but it may be too big an ask even of the 19-time grand slam winner to claim the French Open.

Title wins in Madrid and Rome preceded her 2013 triumph, while in 2002 she also won the event in Rome.

This may be Simona Halep's biggest chance to win her maiden grand slam, having been runner-up to Sharapova last year.

Expect surprises on both sides of the draw with several players enjoying clay more than any other surface.

But all eyes will be on Nadal, particularly throughout the opening rounds when he is expected to cruise.

He will remain the king beyond June 7, but his grip on the throne is ready to be loosened.