Unseeded Coco Gauff advanced to the Italian Open semifinals on Friday when top-seeded Ashleigh Barty retired in the second set with an injured right arm.
Barty, the world No. 1 from Australia, was leading 6-4, 2-1 against the 17-year-old American when she was unable to continue after receiving medical attention.
"It became worse while we were playing," Barty said of the pain in her arm. "So I think that's the challenging thing is to make the decision to stop. It's never nice. It's the thing that I hate the most is not being able to finish a tennis match.
"But the pain was becoming too severe, so it was important that I listen to my body and of course try and do the right thing, knowing that we have a Grand Slam (French Open) in two weeks' time."
Gauff's semifinal opponent Saturday on the red clay in Rome will be either No. 5 seed Elina Svitolina of Ukraine or No. 15 Iga Swiatek of Poland.
No. 9 seed Karolina Pliskova of the Czech Republic and unseeded Croatian Petra Martic will square off in the other semifinal.
Pliskova saved three match points and outlasted Latvia's Jelena Ostapenko 4-6, 7-5, 7-6 (1) in Friday's quarterfinals.
Pliskova made the final four in the Italian capital for a third straight year. The 2019 champion and 2020 runner-up fought off three match points trailing 5-4 in the deciding set before storming back to finish the match in two hours and 20 minutes.
"Just proud, I think mostly, how I fought," Pliskova said. "I'm just happy that I stayed in there and fought till the end."
Each player broke serve seven times and Pliskova finished with nine aces and 13 double faults.
Martic was a 7-5, 6-4 winner against American Jessica Pegula in one hour and 40 minutes. Martic converted only five of her 17 break points, but that was enough to eliminate Pegula -- who knocked out No. 2 seed Naomi Osaka earlier in the week.
"The key was to overtake, to not let her play and take control of the points of the rally and just make me run," Martic said. "So I tried to do that before her. I tried to use my serve. Obviously she didn't like my kick so much, so I knew I had to really be sharp on those first shots after return of serve and not let her overtake. I think I did that pretty well for the most part."
Martic leads Pliskova 4-2 in their head-to-head series and has won both previous meetings on clay.
--Field Level Media