Boisson was one of the four main draw wildcards announced last week along with India No.1 Sahaja Yamalapalli, rising teenage sensation Maaya Rajeshwaran Revathi, and Slovakia ‘s Mia Pohancova, this year’s Wimbledon junior champion.
Sinner, ranked number two in the world, led Italy to a successful defence of its title last year in Spain, but will not be on home soil when the Final 8 takes place in Bologna from November 18-23.
Since winning in Rome in May 2023, Medvedev, ranked 14 in the world, has lost six finals including the US Open the same year, and the Australian Open the following January.
The Danish world number 11 was leading 6-4, 2-2 against Ugo Humbert when he had to retire from the match, adding to a long list of players who have suffered injuries this season.
A 10th career title for Rybakina means the Kazakh only has to reach the semifinals of the Pan Pacific Open in Tokyo this week to seal the last qualifying spot for the season finale at the expense of Russian teenager Mirra Andreeva.
Fernandez, the world number 27, followed up her victory at the DC Open in Washington in July with another tournament win after seeing off qualifier Valentova in Osaka.
