Former US Open finalist Roberta Vinci confirmed her retirement from tennis after losing to Aleksandra Krunic in the first round of the Italian Open in Rome.
Vinci scored one of the biggest upsets in the sport's history when she ended Serena Williams' quest for a calendar grand slam with her semi-final win at Flushing Meadows in 2015.
The 35-year-old home favourite - who also led Italy to four Fed Cup titles - said she was not too disappointed after falling 2-6 6-0 6-3 to the Serbian lucky loser.
Vinci told wtatour.com: "I was happy. I tried to enjoy my game and say thank you to all the people. Here in Rome it was the perfect end to my career."
Rising star Naomi Osaka continued her upward trajectory with an impressive 6-0 6-3 win over former world number one Victoria Azarenka.
Osaka, who won the BNP Paribas Masters in Indian Wells in March, is also growing comfortable on clay and required just 73 minutes to break Azarenka five times and reach round two.
Britain's Johanna Konta beat Magdalena Rybarikova for the second consecutive week to join Osaka in the second round.
Konta beat the Slovakian in straight sets at the Madrid Open last week and she repeated the feat with a 6-4 6-3 win in 10 minutes short of two hours.
Former US Open champion Sloane Stephens came from behind to defeat Barbora Strycova of the Czech Republic and book her place in round two.
Stephens dropped serve twice before losing the first set in a tight tie-break but recovered well to see off the world number 25 6-7 (4/7) 6-3 6-1 in just under two and a half hours.
Thirteenth seed Madison Keys brushed aside Anastasia Pavlyuchenkova 6-4 6-1 but 12th seed Coco Vandeweghe was well beaten 6-1 6-1 by Estonia's Anett Kontaveit.
Other first round winners included qualifiers Donna Vekic and Kaia Kanepi, while former Australian Open finalist Dominika Cibulkova saw off another Italian veteran, Francesca Schiavone, 6-1 6-7 (5/7) 6-2.