Nadal, who a year ago became the first male player to win 11 titles at the same Grand Slam tournament, could meet his old foe Roger Federer in the semifinals.
The third-seeded Swiss will open his quest for a second Musketeers Cup against Italian Lorenzo Sonego, the world number 73, but faces a potentially tricky quarter-final against young Greek Stefanos Tsitsipas who beat him at this year's Australian Open. The 32-year-old Spaniard was forced to delay the start of the season in Brisbane due to a thigh strain and was back at his best at the Australian Open, scoring six commanding wins before a severe loss in the title match against Novak Djokovic, his worst in Major finals.
Defending champion Nadal, seeded second, will open up against a qualifier as he aims for a record-extending 12th title at Roland Garros.
Djokovic, the 2016 champion, is bidding to become only the second man in history to hold all four Slams at the same time.
If Osaka gets by Schmiedlova and reaches the second round, she will face the victor of a blockbuster first-round tilt between 2017 Roland Garros champion Jelena Ostapenko and former World No.1 Victoria Azarenka.
That all changed this season, though, with Nadal losing in the semi-final in three consecutive tournaments on clay and mounting a massive pressure on himself ahead of Rome, the last stop before Roland Garros.
One of the first-round clashes to watch is 2017 champion Jelena Ostapenko against two-times Grand Slam victor Victoria Azarenka, with the victor likely to take on Osaka in the second round.
Defending champion Simona Halep, seeded three, plays Australia's Ajla Tomljanovic in her first round match.
Williams, 38, down at 52 in the world rankings, was runner-up to Serena in 2002.
If the seedings prove an accurate indicator, Osaka would face Australia's Ashleigh Barty in the quarter-finals, Halep would meet two-time Wimbledon champion Petra Kvitova, 2018 runner-up Sloane Stephens would tackle Madrid champion Kiki Bertens while Angelique Kerber of Germany would be Pliskova's last-eight rival. The French Open tennis tournament starts Sunday May 26.
Botswana lifts five-year ban on elephant hunting
There has been disagreement among African leaders over the best course to take when it comes to elephant hunting and ivory sales. Botswana a year ago rejected claims by a leading conservation charity that there had been a surge of elephant poaching.