Rome - Maria Sharapova fired a French Open warning with an epic three-hour win over Roland Garros champion Jelena Ostapenko to reach the Rome semi-finals on Friday as Rafael Nadal continued his clay court domination.
Former world No 1 and five-time Grand Slam winner Sharapova found herself in a dogfight with her Latvian opponent.
Playing her fourth match in as many days, Sharapova needed three hours, 10 minutes to win a gruelling struggle, eventually triumphing 6-7 (6/8), 6-4, 7-5.
For Sharapova, now the world number 40, it was arguably her best victory since her return from a 15-month doping ban last year.
The loss, meanwhile, left Ostapenko with only Rome and Stuttgart quarter-finals to show for her efforts prior to the start of her title defence in Paris a week from Sunday.
Sharapova rode a roller-coaster in her marathon win, working her way from 4-1 down in the first set only to drop it in a tiebreaker after 80 minutes.
She regained her momentum to win the second set but it was tough in the third when she let a 4-2 lead get away.
With Sharapova serving for victory, Ostapenko secured a break for 4-5 thanks to a ninth Sharapova double-fault which yielded a break point.
The sixth seed then saved two Sharapova match points to level 5-5 before the Russian secured victory two games later with a final break in a match marred by 21 cumulative double-faults and a dozen breaks of serve.
Men's top seed Nadal rallied from a set down to post a 4-6, 6-1, 6-2 victory over Italian Fabio Fognini.
Second-ranked Nadal needs to lift an eighth career title at the Foro Italico on Sunday to return to the top of the rankings after losing that position to Roger Federer last week.
Nadal dropped the opening set to Fognini in an hour but regrouped effortlessly as he swept past the Italian in the one-sided second and third sets.
"I'm not used to playing so early," Nadal said of his midday start. "But I'm very happy to be in the semi-finals.
"This was a very important win for me today."
Nadal also beat Fognini in Rome in 2013 in their first ever meeting.
This was his 11th victory in 14 meetings with the 21st-ranked Italian, and sixth in a row.
Nadal is working towards Roland Garros, where he will aim for an unprecedented 11th title.
"My clay court season has been, I think, fantastic. It will be much better if I finish here with another title," added the 16-time Grand Slam winner.
"But I can't forget that I had five months without competing, from Shanghai (October 2017) until Monte-Carlo (last month). I didn't complete - not one event.
"The comeback has been great, I am happy with everything."
It was the first time in four years that Nadal managed to win his quarter-final tie in Rome and next up he will face either fellow former world number one Novak Djokovic or Japan's Kei Nishikori.
Estonian Anett Kontaveit earned an upset over second seed Caroline Wozniacki 6-3, 6-1.
Fourth seed Elina Svitolina recovered from a slow start to defeat former number one Angelique Kerber of Germany 6-4, 6-4.
"I had to really step up and play really aggressive in important moments," Svitolina said. "I think that was the key for today."
Marin Cilic beat Pablo Carreno Busta 6-3, 6-3 to reach the Rome semi-finals for the first time.
Results from the ATP and WTA Masters tournament in Rome on Friday (x denotes seeded player):
Rafael Nadal (ESP x1) bt Fabio Fognini (ITA), 4-6, 6-1, 6-2
Marin Cilic (CRO x4) bt Pablo Carreno Busta (ESP x10) 6-3, 6-3
Maria Sharapova (RUS) bt Jelena Ostapenko (LAT x5) 6-7 (6/8), 6-4, 7-5
Elina Svitolina (UKR x4) bt Angelique Kerber (GER) 6-4, 6-4
Anett Kontaveit (EST) bt Caroline Wozniacki (DEN x2) 6-3, 6-1