PARIS -- Playing in his first Grand Slam match since becoming a major champion, Stan Wawrinka lost.
The Australian Open champion was on center court Monday at the French Open, but he was eliminated in the first round after losing to 41st-ranked Guillermo Garcia-Lopez of Spain 6-4, 5-7, 6-2, 6-0.
Wawrinka had 61 unforced errors and won only 54 percent of the points on his first serve.
Both former No. 1 players advanced to the second round at Roland Garros, playing through rain and rain delays, while current No. 1 Nadal finished off his match in the sunshine.
Djokovic beat Joao Sousa of Portugal 6-1, 6-2, 6-4 despite being broken three times, including while serving for the match for the first time.
The second-seeded Serb was leading 4-1 when rain halted play on Court Philippe Chatrier, but it restarted about an hour later.
"Very heavy conditions. The court is not that great, in a great condition, at this moment," Djokovic said. "But of course, considering the amount of the rain that we had in last four or five days, it is not easy for people to maintain the court in the right state. They are doing their best."
In the second set, a short shower stopped play for only a few minutes. Djokovic, wearing a white rain jacket, used the time to entertain the crowd by chatting with a ball boy and letting the youngster sit alongside him on the bench.
At one point, Djokovic grabbed the umbrella out of the ball boy's hand and in return gave him a racket. Then Djokovic handed him a bottle of Perrier, and the two clinked bottles before taking a sip.
"We had a nice chat. He's a tennis player, so I asked him how long he's playing, and how he's enjoying his time as a ball kid," Djokovic said. "It was a nice, fun time, something unusual for the Grand Slams."
Djokovic can complete a career Grand Slam by winning the French Open.
Nadal has already won a record eight French Open titles, but he is looking to become the first man to win five times in a row in Paris.
On Monday, he improved his record at Roland Garros to 60-1 by beating Robby Ginepri of the United States 6-0, 6-3, 6-0.
"Always the same: To win against anyone I need to play at a good level and I need to be ready for fight and for everything that I will need to do to win," said Nadal, looking ahead to his next match.
Sharapova, the 2012 champion, was first on court in the main stadium and needed little more than an hour to beat Ksenia Pervak 6-1, 6-2. She broke Pervak five times and finished with 17 winners, while Pervak had only four.
Sharapova, seeded seventh at the French Open, completed a career Grand Slam at Roland Garros two years ago. She then lost to Serena Williams in the 2013 final.
Up next in Paris will be Tsvetana Pironkova of Bulgaria in the second round. But she could face Williams in the quarterfinals.
"It's tough to think about that match down the line where you have to compete in three matches before that," Sharapova said. "Obviously it's a match that many people always look forward to when we play against each other."
Monday's match started about 1 hour, 20 minutes late because of the wet weather. The forecast calls for more rain for the rest of the week.
Other winners include No. 5 Petra Kvitova of the Czech Republic, No. 12 Flavia Pennetta of Italy, No. 16 Sabine Lisicki of Germany, No. 17 Roberta Vinci of Italy, No. 18 Eugenie Bouchard of Canada, No. 19 Samantha Stosur of Australia, No. 20 Alize Cornet of France, No. 28 Andrea Petkovic and No. 32 Elena Vesnina of Russia.
No. 14 Fabio Fognini of Italy, No. 17 Tommy Robredo of Spain, No. 18 Ernests Gulbia of Latvia, No. 25 Marin Cilic of Croatia, No. 26 Feliciano Lopez of Spain, No. 27 Roberto Bautista Agut of Spain and No. 29 Gilles Simon of France advanced, while No. 30 Vasek Pospisil of Canada lost.