Maria Sharapova suffered defeat in her only match in the Tie Break Tens on Thursday, as Simona Halep and Grigor Dimitrov triumphed in Madrid.
Sharapova made her comeback following a 15-month ban for failing a drugs test last week, reaching the semi-finals at the Stuttgart Open, a performance that saw her re-enter the WTA rankings at number 262.
But the five-time grand slam champion and former world number one could not live with Monica Puig at the exhibition event, in which a field of eight compete in matches consisting of a first to 10 tie-break.
Puig forged a 7-2 lead that she did not relinquish, claiming a 10-6 win, leaving Sharapova to rue a slow start.
Puig could not carry her form into the semi-finals, though, suffering defeat to Halep, who dictated matters from the baseline in her 10-6 triumph over Svetlana Kuznetsova in the final.
England hold their nerve to make it through to the World Cup Final at a sold-out Lord's on Sunday.