Osaka, who has won the past two Grand Slams – the US Open in September 2018 and the Australian Open in January – had appeared in big trouble when she surrendered the first set to Slovakian Anna Schmiedlova 6-0.

The Japanese battled through a tense tie-break to level the match before running away with the third set to clinch a 0-6, 7-6, 6-1 victory in just under two hours.

She will face Victoria Azarenka in round two after the Belarussian former world number one won 6-4, 7-6 against Latvian Jelena Ostapenko.

Third seed Simona Halep also made hard work of her first-round tie with Ajla Tomjanovic, but having been pegged back to one set all, the diminutive Romanian raced away with the deciding set to win 6-2, 3-6, 6-1.

Men's fifth seed Alex Zverev had to battle for his place in round two against Australian John Millman.

Zverev won the Next Gen tournament in Milan in 2017 and has been tipped for Grand Slam success since, but as yet, that form has failed to materialise in a two-week Grand Slam.

Having raced into a two-set lead, Zverev lost his cool and smashed his racquet as world number 56 Millman levelled the match at two sets each.

The German battled through the final set to seal a 7-6(4), 6-3, 2-6, 6-7 (5-7), 6-3 win and set up a clash with Mikael Ymer.

Argentine Juan Martin del Potro had to come from a set down against Czech Nicolas Jarry to progress, but sealed a 3-6, 6-2. 6-1. 6-4 victory.

Eighth seed Fabio Fognini overcame compatriot Andreas Seppi 6-3, 6-0, 3-6, 6-3 while Lucas Pouille, seeded 22, had home support on his side as he cruised to a 6-3, 6-4, 7-5 win against Simone Bolelli.

There was more home delight for French qualifier Elliot Benchetrit, who enjoyed a straight sets 6-3, 6-0, 6-2 win against Cameron Norrie. 

The 20-year-old reached the main draw when controversial Australian Nick Kyrgios withdrew citing illness just days after criticising the tournament on social media.

In a match carried over from Monday, Briton Kyle Edmund edged out Jeremy Chardy 7-5 in the deciding fifth set to record a 7-6, 5-7, 6-4, 4-6, 7-5 win. 

Elsewhere, Ivo Karlovic won the battle of the big hitters as he recorded a 7-6 (4), 7-5, 6-7 (7-9), 7-5 triumph against Spain's Feliciano Lopez.

Women's 17th seed Anett Kontaviet was sent packing by world number 73 Karolina Muchova.

Estonian Kontaviet took the first set 6-3 but Muchova fought back for a 3-6, 6-2, 6-2 victory.

The men's doubles draw opened up with Italian duo Matteo Berrettini and Lorenzo Sonego ousting second seeds Jamie Murray and Bruno Soares 4-6, 7-5, 7-6 (4).