Osaka of Japan confirmed last week that she will not be carrying out all her media duties at Roland Garros, citing mental health concerns as the reason for her boycott.

But the four-time major champion was fined $15,000 (£10,570/€12,302) after refusing to "honour her contractual media obligations" following her 6-4, 7-6 (7-4) victory over Patricia Maria Tig of Romania in Paris today.

A lengthy joint statement from the four Grand Slam organisers said the mental health of players was of the "utmost importance" but insisted "a core element" of regulations for players at majors is to engage with the media "whatever the result of their match".

"These interactions allow both the players and the media to share their perspective and for the players to tell their story," the statement read.

"The facilitation of media to a broad array of channels, both traditional and digital, is a major contributor to the development and growth of our sport and the fan base of individual players.

"We have advised Naomi Osaka that should she continue to ignore her media obligations during the tournament, she would be exposing herself to possible further Code of Conduct infringement consequences.

"As might be expected, repeat violations attract tougher sanctions including default from the tournament (Code of Conduct article III T.) and the trigger of a major offence investigation that could lead to more substantial fines and future Grand Slam suspensions (Code of Conduct article IV A.3.).”

"We want to underline that rules are in place to ensure all players are treated exactly the same, no matter their stature, beliefs or achievement.  

"As a sport there is nothing more important than ensuring no player has an unfair advantage over another, which unfortunately is the case in this situation if one player refuses to dedicate time to participate in media commitments while the others all honour their commitments."

The biggest shock on the court on day one of the tournament was caused by veteran Spaniard Pablo Andujar after toppling Dominic Thiem of Austria.

The 35-year-old came from two sets down to beat two-time runner-up and the world number four 4-6, 5-7, 6-3, 6-4, 6-4 in the first round.

"It is very special to win here at Roland Garros," said Andujar.

"[It was] such an emotional win for me, being two-sets-to-love down against an amazing player."

It was only the second time that Thiem had lost from two sets up, following on from his 2017 US Open fourth-round defeat to Juan Martin del Potro of Argentina.

Germany's Alexander Zverev looked set to follow Thiem through the exit door as he lost the first two sets against countryman Oscar Otte before rallying to win 3-6, 3-6, 6-2, 6-2, 6-0.

Fifth seed Stefanos Tsitsipas of Greece enjoyed a more comfortable passage beating France's Jeremy Chardy under the floodlights 7-6, 6-3, 6-1.

Italian number 27 seed Fabio Fognini struck 31 winners in a 6-4, 6-1, 6-4 victory over French wildcard Gregoire Barrere in two hours and eight minutes.

Fognini now plays Hungary’s Marton Fucsovics, who beat Gilles Simon of France 6-4, 6-1, 7-6 (7-5) over three hours and 13 minutes.

Former world number four Kei Nishikori battled from a break down in the decider to defeat Italian Alessandro Giannessi 6-4, 6-7 (7-4), 6-3, 4-6, 6-4.

The Japanese star will next play Russian 23rd seed Karen Khachanov, who dismissed Czech ace Jiri Vesely 6-1, 6-2, 6-3.

Earlier in the day, Roberto Bautista-Agut defeated fellow Spaniard Mario Vilella Martinez 6-4, 6-4, 6-2, while Britain’s Dan Evans - who has been in fine form on clay this season - suffered a 1-6, 6-3, 6-3, 6-4 defeat to Miomir Kecmanović of Serbia.

In the women’s event, Petra Kvitova of the Czech Republic saved a match point to overcome Belgian qualifier Greet Minnen, 6-7 (3-7), 7-6 (7-5), 6-1 and avoid a first opening-round exit at the French Open in 11 years.

Third seed Aryna Sabalenka of Belarus needed just 75 minutes to see off Croatia's Ana Konjuh, 6-4, 6-3.

Fellow Belarusian Victoria Azarenka emerged the victor in a battle between two Grand Slam champions.

Azarenka eliminated Svetlana Kuznetsova of Russia 6-4, 2-6, 6-3 to book a spot in the second round in Paris.

Former world number one Angelique Kerber of Germany was upset in her opening-round, losing 6-2. 6-4 to Ukrainian qualifier Anhelina Kalinina.