The most intriguing women's match on the card in Rome has ended prematurely with Emma Raducanu forced to retire with a back injury.
The reigning US Open champion was losing 6-2 2-1 to the 2019 winner, Bianca Andreescu, who was also born in Canada with Romanian heritage.
Raducanu, who has been dogged by a series of injuries this season - her first full-time campaign - told a physio on Tuesday: "I can't move" before quitting.
A one-sided first set saw Raducanu have no answer to Andreescu's power while struggling to make her own serve count.
Raducanu spent some time off the court for treatment and she was clearly uncomfortable when play got back under way.
Andreescu, herself working her way back to form after taking a break for mental health reasons and a knee injury, now faces Spain's Sara Sorribes Tormo.
Overnight Ajla Tomljanovic moved into the second round when her opponent Camila Giorgi retired. The Italian had been struggling with a calf injury when rain forced the suspension of the match on Monday night with the Australian No.1 winning 6-3 4-2.
Tomljanovic next faces Ons Jabeur, winner in Madrid on Sunday, after the Tunisian brushed aside Sorana Cirstea 6-0 6-.
Two 2017 champions both lost. Sloane Stephens, the US Open winner, was beaten 6-1 6-2 by Ekaterina Alexandrova. American qualifier Lauren Davis defeated French Open champion Jelena Ostapenko 6-2 6-3.
In the WTA 125 event at Karlsruhe, Germany, Australia's Priscilla Hon has reached the last 16, coming from behind to beat France's Clara Burel 3-6 6-2 7-6 (8-6).
But there was no Aussie success at the WTA 125 Trophee Lagardere in Paris.
Daria Savile lost a titanic three hour, 15 minutes battle with Brazil's Beatriz Haddad Maia 7-5 6-7 (3-7) 7-6 (7-4). Maddidson Inglis perished far more quickly to France's Diane Parry, 6-1 6-4.