Novak Djokovic is into his record 10th consecutive French Open quarterfinal, something not even King of Clay Rafael Nadal has managed to do.

And Djokovic is yet to be challenged at all this year at Roland Garros. Not only hasn't he lost a set — he's only twice ceded as many as four games in a set.

Extending his Grand Slam winning streak to 25 matches and closing in on a fourth championship in a row, Djokovic was dominant yet again in the fourth round Monday, beating 45th-ranked Jan-Lennard Struff of Germany 6-3, 6-2, 6-2.

"Everything is coming together beautifully. I'm motivated to fight for the trophy, yes. I mean, that's why I'm here," said Djokovic, who owns 15 Slam titles, including one in Paris. "But it's still a long way to go."

It's helped, certainly, that the No. 1-ranked Djokovic has not needed to deal with a single seeded foe yet. That will change now: He faces No. 5 Alexander Zverev for a spot in the semifinals.

Have things been too easy so far? Is it possible that Djokovic hasn't had the proper preparation for what could be tougher going in the latter portion of the tournament?

"I don't mind cruising along, to be honest," he said with a smile. "I have plenty of experience, I think, dealing with situations where you're facing break points or where it's tense. I have played plenty of, I think, tight matches in my career, that I can rely on that experience."

He added: "It's good to be tested, from that perspective, but at the same time, it's also good to cruise along and kind of conserve the energy for what's coming up."

Djokovic and Zverev have split four previous tour meetings.

Zverev reached his second straight quarterfinal in Paris by coming back to eliminate No. 9 Fabio Fognini 3-6, 6-2, 6-2, 7-6 (5).

He's only 22, but Zverev has been touted as a future champion for quite some time. He has yet to play in a major semifinal, though, and mentioned Monday that he enjoyed getting to be a bit under the radar so far in this French Open, noting that 20-year-old Stefanos Tsitsipas, the sixth seed, was a subject of more focus until losing in the fourth round to Stan Wawrinka.

"For me," Zverev said, "it was actually quite a nice thing that not all of the attention ... is only going towards my way."

Unlike Djokovic, he has not exactly had an easy path to the round of eight: Zverev needed to win two five-setters in addition to going four against Fognini.

The other quarterfinal on their half of the draw Wednesday will be No. 4 Dominic Thiem against No. 10 Karen Khachanov, who got past 2009 U.S. Open champion Juan Martin del Potro 7-5, 6-3, 3-6, 6-3 to make it to the final eight for the first time at a major.

Thiem advanced by eliminating the last Frenchman in the field, No. 14 Gael Monfils, 6-4, 6-4, 6-2. A man from the host country hasn't won the French Open since Yannick Noah in 1983.

Rain is forecast for Tuesday, when the men's quarterfinals will be Roger Federer vs. Wawrinka, and Nadal vs. No. 7 Kei Nishikori, who completed his two-day 6-2, 6-7 (8), 6-2, 6-7 (8), 7-5 fourth-round victory over Benoit Paire of France.