Paris: Serena Williams announced her shock withdrawal from the French Open through injury on Monday just minutes before her scheduled fourth-round clash against Maria Sharapova.
The 36-year-old said she had suffered a pectoral muscle injury in her third-round win over Julia Goerges and "can't serve at all".
The 23-time Grand Slam champion added that she would stay in Paris for a Tuesday scan on the injury.
"I, unfortunately, have been having some issues with my pec muscle, and (it) has been getting worse to the point where right now I can't actually serve. It's kind of hard to play when I can't physically serve," she explained.
She was unable to say whether or not she would be fit for Wimbledon which gets underway in four weeks' time.
"I'm beyond disappointed," added three-time Roland Garros champion Williams who was playing in her first Grand Slam since winning the 2017 Australian Open while two months pregnant.
She was also in just her third tournament of the year after giving birth to daughter Olympia in September.
"I gave up so much time with my daughter and time with my family all for this moment. So it's really difficult to be in this situation."
Williams, whose absence from the sport has seen her ranking tumbling to 451, has not lost to the Russian since 2004, winning their last 18 matches.
It had been the most eagerly-awaited match of the tournament, coming just two days after Williams had blasted Sharapova's autobiography for being "100 percent hearsay" when it came to references about her.
"I think Serena hated me for being the skinny kid who beat her, against all odds, at Wimbledon," Sharapova wrote in 'Unstoppable'.
"Not long after I heard Serena told a friend, who then told me, 'I'll never lose to that little bitch again'."
'Sacrificed so much'
Sharapova, the champion in Paris in 2012 and 2014, goes on to play a first quarter-final at the Slams since losing to Williams at the same stage at the 2016 Australian Open.
It was in Melbourne that Sharapova tested positive for meldonium after which she served a 15-month doping ban.
The Russian will face 2016 champion Garbine Muguruza who was 2-0 ahead or Lesia Tsurenko when the Ukrainian quit having suffered a leg injury.
"I was looking forward to my match against Serena and am disappointed that she had to withdraw," said Sharapova in a statement.
"I hope she returns to the tour soon."
Despite playing just four matches in 2018 before Roland Garros, Williams played doubles in Paris with sister Venus.
They had been knocked out on Sunday by Andreja Klepac and Maria Jose Martinez Sanchez with the American sisters getting a 6-0 bagel in the final set.
Serena had gone into that match wearing her striking all-black catsuit but admitted she had had to tape her serving arm to try and protect the injury.
"Every match has been getting better for me. Physically I'm doing great," she said.
"I sacrificed so much to be at this event. I can only take solace in the fact I'm going to continue to get better.
"And I had such a wonderful performance in my first Grand Slam back."
However, her status for Wimbledon where she has been champion seven times, will only become clear once she has had an MRI.
"I made a promise that if I'm not at least 60 percent or 50 percent, then I probably shouldn't play," she added.
Serena's withdrawal completely over-shadowed the remainder of Monday's last-16 programme.
World No 1 Simona Halep, twice a runner-up, needed less than an hour to make the last-eight for the third time with a 6-2, 6-1 rout of Belgium's Elise Mertens.
"I was a little bit stronger in the important moments," said Halep who next faces 12th seed Angelique Kerber.
The German, a former World No 1 and a two-time major winner, reached the quarter-finals for the second time with a 6-2, 6-3 win over France's Caroline Garcia.
Australian Open champion and second seed Caroline Wozniacki was knocked out by Russia's Daria Kasatkina 7-6 (5), 6-3.
Kasatkina will be playing in her first Slam quarter-final where she will face US Open champion Sloane Stephens.
Updated Date: Jun 05, 2018 00:19 AM