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.
Sharapova falls at the first hurdle. Olympic champion Monica Puig's aggressive play gets the better of Sharapova guiding her to victory 10-6 pic.twitter.com/H0bJJkHID2-- Tie Break Tens (@tiebreaktens) May 4, 2017
"It was a lot more fun than I expected, I love the format, I love how quick it is," Sharapova said afterwards.
"You want to get off to a good start, I think that's probably of importance in a regular tie-break and a tie-break to 10, that's certainly the key.
"In a quick format like that you've got to get ready, which I wasn't."
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.
On the men's side Dimitrov saw off Feliciano Lopez 10-7, having earlier beaten Fernando Verdasco and Dan Evans.