Rafael Nadal of Spain returns a shot during the men's singles 4th round match against Maximilian Marterer of Germany at the French Open Tennis Tournament 2018 in Paris, France, on June 4, 2018. Rafael Nadal won 3-0. (Xinhua/Luo Huanhuan)

Rafael Nadal of Spain returns a shot during the men's singles 4th round match against Maximilian Marterer of Germany at the French Open Tennis Tournament 2018 in Paris, France, on June 4, 2018. Rafael Nadal won 3-0. (Xinhua/Luo Huanhuan)

Rafael Nadal of Spain returns a shot during the men's singles 4th round match against Maximilian Marterer of Germany at the French Open Tennis Tournament 2018 in Paris, France, on June 4, 2018. Rafael Nadal won 3-0. (Xinhua/Luo Huanhuan)

Rafael Nadal of Spain returns a shot during the men's singles 4th round match against Maximilian Marterer of Germany at the French Open Tennis Tournament 2018 in Paris, France, on June 4, 2018. Rafael Nadal won 3-0. (Xinhua/Luo Huanhuan)

Rafael Nadal of Spain returns a shot during the men's singles 4th round match against Maximilian Marterer of Germany at the French Open Tennis Tournament 2018 in Paris, France, on June 4, 2018. Rafael Nadal won 3-0. (Xinhua/Luo Huanhuan)

Simona Halep of Romania serves during the women's singles 4th round match against Elise Mertens of Belgium at the French Open Tennis Tournament 2018 in Paris, France on June 4, 2018. Simona Halep won 2-0. (Xinhua/Luo Huanhuan)(wll)

Simona Halep of Romania returns the ball during the women's singles 4th round match against Elise Mertens of Belgium at the French Open Tennis Tournament 2018 in Paris, France on June 4, 2018. Simona Halep won 2-0. (Xinhua/Luo Huanhuan)(wll)

Simona Halep of Romania eyes on the ball during the women's singles 4th round match against Elise Mertens of Belgium at the French Open Tennis Tournament 2018 in Paris, France on June 4, 2018. Simona Halep won 2-0. (Xinhua/Luo Huanhuan)(wll)

Simona Halep of Romania celebrates after winning the women's singles 4th round match against Elise Mertens of Belgium at the French Open Tennis Tournament 2018 in Paris, France on June 4, 2018. Simona Halep won 2-0. (Xinhua/Luo Huanhuan)(wll)

Rafael Nadal of Spain returns a shot during the men's singles 4th round match against Maximilian Marterer of Germany at the French Open Tennis Tournament 2018 in Paris, France, on June 4, 2018. Rafael Nadal won 3-0. (Xinhua/Luo Huanhuan)