Australian Open champion Stanislas Wawrinka crashed out of the French Open in a huge first-round shock at Roland Garros.

The third seed never looked comfortable in heavy conditions after a wet day in Paris and fell 6-4 5-7 6-2 6-0 to Spain's Guillermo Garcia-Lopez.

It was a nasty first-round draw against a very capable clay-courter but few would have predicted an upset nor the abject form Wawrinka showed for much of the match.

When the 29-year-old won the Masters title in Monte Carlo last month it looked like he could potentially add the French Open crown to the one he so stunningly won in Melbourne in January.

But he was in trouble virtually from the start on Court Philippe Chatrier and became the first Australian Open champion to lose in the first round in Paris since Petr Korda in 1998.

Wawrinka, who has struggled at times with his new status as a major winner, made the quarter-finals in Paris last year for the first time having reached the fourth round in the previous three years.

A disappointed Wawrinka said afterwards: "I was completely flat. I was not really relaxed with my game. I wasn't aggressive. I was playing some bad rallies. Everything was terrible.

"I always put a lot of pressure on myself. But before the match and during the match it was not really about only the pressure.

"I think it's just a different story. Now it's a different picture for my career. I need to put the puzzle back together, but differently than in the past.

"Because now it's after winning grand slam, Masters 1000, being number three in the world. Everything is different, and I still didn't find all the pieces."

Rafael Nadal found Court Suzanne Lenglen to his liking as he dispatched American wild card Robby Ginepri.

Many eyebrows were raised when the order of play for Monday was released showing the eight-time champion would be opening his campaign on Roland Garros' second court.

The other grand slams do not have hard and fast rules like Wimbledon, where the defending champions open play on Centre Court on the first two days.

But for the man who has lost only once in nine years in Paris and is the world number one to be treated in such a manner was certainly unusual.

Nadal's camp let it be known on Sunday night that they were not happy, but in the end the 27-year-old spent only an hour and 42 minutes out there on his way to a 6-0 6-3 6-0 victory.

Ginepri reportedly headed to the venue early in the morning on Sunday to practise on Court Philippe Chatrier in the assumption he would be playing there.

The 31-year-old certainly needed to familiarise himself with such surroundings having not played in the main draw in Paris since 2010.

Later that year Ginepri, a former top-15 player, broke his elbow after falling off his bicycle and he has not been back in the top 100 since.

Nadal was therefore the last man he would have wanted to be drawn against, and the Spaniard, looking to become the first man to win five successive French Open titles, was typically ruthless.

Ginepri enjoyed a decent spell early in the second set but could make no headway on Nadal's serve and found his own under constant pressure.

Nadal is likely to find things tougher in the second round, where 20-year-old rising star Dominic Thiem will be his opponent.

Novak Djokovic kicked off his bid for a maiden title at Roland Garros with a comfortable win over Joao Sousa.

The French is the only grand slam that does not sit in Djokovic's trophy cabinet and he has been widely tipped to amend that over the coming weeks - largely due to Nadal's recent failures on the red surface.

Sousa did little to stop him in this one, with Djokovic winning 6-1 6-2 6-4 - as easily as he did when the two met at the US Open last year.

There was enough to suggest that Djokovic may not be as good a bet as had been claimed, though, with a number of loose shots and concentration lapses likely to be noted by the Nadal camp.

That Djokovic stopped chasing balls down in the third set will be of particular concern to him and coach Boris Becker, with the match going on for far longer than it should have done.

Djokovic made his mark on the match early on, eventually breaking at the end of a nine-minute second game when Sousa netted a forehand to cash in a fifth break point.

He held to love and then broke again, this time at the first attempt, as his opponent planted a two-hander wide.

Sousa would at least respond with a break of his own before a lengthy rain delay, but offered his serve up again on the other side of it.

Not entirely settled on his own delivery Djokovic then went three break points down as he looked to close out the set, but recovered with five points in a row.

The second set started a little tighter but the six-time major winner got the break he was looking for in the fifth game, Sousa double-faulting on break point.

That became a double break as the Serb upgraded a second bonus point when Sousa put a forehand wide, before the rain came again. The players did not leave the court this time and Djokovic entertained the crowd by inviting a ball boy to sit with him under his umbrella.

He had to sharpen up after the restart as he went a break point down but quickly did so and took the set 6-2.

Sousa appeared to be done for now and lost his serve in the third game of the next set, slapping a forehand into the net, and also in the fifth via a brilliant forehand.

The Portuguese did fashion two break points back, though, and took the second of them as Djokovic relaxed. The world number two responded with another break but then lost his own serve as he looked to serve his way into the next round.

Sousa kept it alive for another game, with Djokovic showing minimal interest in returning his shots before finally getting the job done.

Joining Wawrinka in exiting the tournament was ninth seed Kei Nishikori, who had been a doubt because of a back injury and went out 7-6 (7/4) 6-1 6-2 to Martin Klizan of Slovakia.

The Japanese player has been one of the stars of the season and had led Nadal by a set and a break in the Madrid final earlier this month before being struck down with the back problem.

There was a remarkable win for Argentinian qualifier Facundo Bagnis, who marked his grand slam debut by defeating France's Julien Benneteau 6-1 6-2 1-6 3-6 18-16, equalling the most games in a final set at the French Open.

There were also wins for Fabio Fognini, Marin Cilic, Ernests Gulbis and Gilles Simon.