Martina Hingis and Kim Clijsters have both qualified for the season-ending WTA Championship next month.
Hingis is in her comeback season
Their participation was confirmed when Swiss Patty Schnyder lost to Russia's Maria Sharapova in the semi-finals of the Linz Open in Austria on Saturday.
The top eight players in the WTA rankings qualify for the tournament.
The pair will join Amelie Mauresmo, Justine Henin-Hardenne, Maria Sharapova, Svetlana Kuznetsova, Nadia Petrova and Elena Dementieva in Madrid.
The championship starts on 7 November.