Top seed will take on Germany's Kerber, who ended French hopes by eliminating Garcia, while Russian pair Kasatkina and Sharapova also took their places in the next round
Simona Halep headlines French Open quarter-finals as Serena Williams withdrawal overshadows fourth-round action
World No 1 Simona Halep spearheads Tuesday's French Open quarter-final line-up after Monday's highly-anticipated fourth round clash between Serena Williams and Maria Sharapova fell through moments before the pair were due on court.
Romanian top seed Halep was in ruthless form against Belgian 16th seed Elise Mertens, claiming a 6-2, 6-1 win to reach the last-eight where she will face Angelique Kerber. The German 12th seed ended French hopes by eliminating seventh seed Caroline Garcia 6-2, 6-3.
Russia's Daria Kasatkina is also through to the quarter-finals after claiming her third win of the season over second seed Caroline Wozniacki. The 14th seed, who reached the final of the Dubai Duty Free Tennis Championships in February, ran out a comfortable 7-6, 6-4 winner and will take on American Sloane Stephens for a place in the semi-finals.
However, the big story from Paris on Monday focused on a match that didn't even go ahead after three-time Roland Garros champion Williams withdrew from her last-16 clash with long-time rival Sharapova.
Williams, 36, 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 scan on Tuesday to assess the extent of 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," Williams said.
She was unable to say whether or not she would be fit for Wimbledon, which gets underway in four weeks' time and where Williams is a seven-time champion.
"I'm beyond disappointed," added 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."
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 per cent hearsay" when it came to references about her.
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 either 2016 champion Garbine Muguruza or Lesia Tsurenko of Ukraine for a semi-final place.
"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."
While Sharapova continues her quest for a third Roland Garros title, top seed Halep is seeking her first, and on the form she has displayed in the French capital, she will be confident of ending her wait for a grand slam title - even if she admits to battling with nerves before matches.
"I don't know how the other players are before the matches, but I think I am very nervous before every match, and this is because I am like this," Halep, 26, said.
"So I'm not going to fight with myself about that. But I try to improve this thing, and I try to enjoy my nerves, because they are special when you play in a grand slam."
Halep's quarter-final opponent Kerber also produced an impressive performance, setting up a clash between two in-form players for a place in the semi-finals.
The German former world No 1, seeded 12th, played from the back of the court throughout her win over Garcia, making it impossible for her 24-year-old opponent to develop her attacking game.
Double grand slam champion Kerber only hit 11 winners but Garcia made 36 unforced errors, meaning the German was never under too much pressure.
Garcia had reached two semi-finals in top-tier events on clay this season, but in front of her home fans on Court Suzanne Lenglen she was unable to produce her best tennis.
The Frenchwoman briefly threatened a comeback when she pulled a break back for 5-3 after saving four match points, but then sent a routine forehand wide on the fifth match point in the following game.
"I'm happy to be through, she has played really well in the last few months," Kerber said of Garcia, who had reached the quarter-finals last year.
All of the French players in the men's singles draw were knocked out of the tournament before reaching the fourth round.