Barty and Osaka have spent much of 2019 battling it out for the World No.1 spot in the WTA rankings, having won Roland Garros and the Australian Open respectively. Barty currently holds top spot.
Petra Kvitova and Belinda Bencic complete the draw for the red group.
In the other round-robin group, the eye-catching clash was that of Simona Halep and Bianca Andreescu, the winners of the Wimbledon and US Open titles.
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They will also have to tackle World No.2 Karolina Pliskova and defending champion Elina Svitolina.
The WTA Finals are taking place in Shenzhen for the first time ever, with Svitolina winning the last edition of the event held in Singapore.
Elsehwere, Barty has been confirmed as the winner of the Race to Shenzhen, having accumulated the most rankings points in the year to date.
Pliskova finished second in the race, with over 1100 points fewer than her rival, having played four extra tournaments.
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