PARIS — Rafael Nadal’s strokes are always accompanied by lots of grunting, so the French Open must be more difficult than his results make it look.

Still unbeaten at Roland Garros, Nadal completed the men’s quarterfinal field yesterday by sweeping Lleyton Hewitt 6–3, 6–1, 7–6 (5).

The two-time defending champion is 18–0 lifetime at the French Open, which seems to be getting easier for him: For the first time, he reached the final eight without losing a set.

“I played my best match of the tournament,” Nadal said. “Lleyton is always a very good test and a very tough match because he is a winner. I’m happy with my game today.”

A potential showdown looms Sunday between the no. 2-seeded Nadal and top-ranked Roger Federer, who seeks his first French Open title to complete a career Grand Slam.

Nadal’s opponent tomorrow will be fellow Spaniard Carlos Moya, the 1998 champion.

“I prefer to lose against him than against any other player because he is a great friend,” Nadal said. “He did a lot of things for me when I arrived on the men’s circuit.”

Moya declined to take credit for Nadal’s dominance.

“I don’t think he learned anything from me,” Moya said. “And if he did, he did it much better than me.”

The other quarterfinal tomorrow will be between No. 125-ranked Igor Andreev and No. 6-seeded Novak Djokovic.

Andreev, who eliminated No. 3-seeded Andy Roddick in the opening round, advanced to his first major quarterfinal by rallying past No. 16 Marcos Baghdatis 2–6, 6–1, 6–3, 6–4. Djokovic swept unseeded Fernando Verdasco 6-3, 6-3, 7-6 (1) to reach the final eight for the second consecutive year.

“Last year, I honestly didn’t expect to be in the quarterfinals,” the 20-year-old Djokovic said. “I was pretty much satisfied with my achievement. This year is much different.”

The marquee pairing in the women’s quarterfinals Tuesday features two-time defending champion Justine Henin against eight-time Grand Slam champion Serena Williams. It’s a rematch of their contentious 2003 semifinal at Roland Garros.

Hewitt had beaten Nadal in four of their six previous meetings, but on clay the matchup of baseliners was a mismatch from the outset. Nadal won 16 of the first 20 points.

“He just hits the ball so much differently to anyone out there,” Hewitt said. “His spin off his forehand — it’s quite amazing. He can really work it over.”

The no. 14-seeded Hewitt led for most of the third set and held advantages of 4–2 and 5–4 in the tiebreaker. But he blew an easy forehand to make it 5-all, then netted another easy forehand on the final point.

Nadal displayed racket wizardry even between points, when he drew applause for an over-theshoulder catch on the strings of a ball lobbed from the other end of the court. He’s bidding to become the first man to win a third consecutive French Open title since Bjorn Borg was champion in 1978-81.

Moya overcame his relative inexperience to beat Jonas Bjorkman. A Roland Garros perennial, Moya was nonetheless the younger player Monday, and he swept the 35-year-old Bjorkman 7–6 (5), 6–2, 7–5.

Wearing a sleeveless shirt and his cap backward, the 30-year-old Moya hardly looked like an oldtimer. But he became the oldest man to reach the final eight at the French Open since Andre Agassi in 2003.

Moya has won two of his previous five matches against Nadal.

“It’s going to be a beautiful match to play,” Moya said, “and very tough for both of us.”

Once ranked no. 1, Moya is playing in the tournament for the 12th year in a row.

“Now I’m the oldest guy in the field,” he said. “I still remember when I was the youngest guy in the draw, and now I became the oldest. Time passed so fast. … When you’re younger, maybe you don’t value things as I do now. I enjoy more now.”

Bjorkman, the oldest man in the 128-player draw, overcame deficits of two sets to none in the first two rounds. But this time he was the one squandering leads.

The unseeded Swede was ahead 5-2 in the opening set but lost the next four games. He broke serve for 6-all and led 5-3 in the tiebreaker before Moya swept the final four points, the last with a net cord winner.

Bjorkman began to show signs of wear after losing the second set, when he needed a shoulder massage from a trainer.

“You know, I’m 35,” Bjorkman said. “My shoulder just got more tired than it normally does. … This is a great day. I obviously surprised myself to make the fourth round.”

He lost serve in the final game, pushing a tired backhand into the net on match point.

The no. 23-seeded Moya, long known for his Popeye-size right biceps, hit 21 forehand winners to three for Bjorkman, and the disparity helped the Spaniard save 11 of the 14 break points he faced.

Like Moya, the No. 6-seeded Djokovic benefited from a lucky bounce on an important point. It came in the tiebreaker, when his backhand kissed the net cord before dropping for a winner.

Djokovic crossed himself in gratitude. Verdasco retrieved the ball and put it in his courtside bag, prompting laughter from the crowd.