PARIS — King of clay Rafael Nadal and 20-time Grand Slam winner Roger Federer were given workouts by German qualifiers, but both safely advanced in straight sets into the third round of the French Open on Wednesday.

Yannick Maden, ranked 114th, broke 11-time champion Nadal twice in a fiercely contested third set on a sunny afternoon on Court Suzanne Lenglen, before eventually succumbing 6-1, 6-2, 6-4, in 2 hours, 9 minutes.

"It was a good match for the first two sets. Not unbelievable, but with positive feelings," Nadal said. "Then in the third I think I lost a little bit of concentration and intensity. And then the match became difficult. That's all.

"That's just about concentration, my feeling, because the feeling on the match had been positive. Positive thing is every time that I had the mistake, then I had the break again, and that's the good news."

Shortly afterward 144th-ranked Oscar Otte refused to be intimidated by the packed 15,000-seat Philippe Chatrier centre court and by Federer's aura as he impressed with huge ground strokes and big serves before losing 6-4, 6-3, 6-4.

Federer, back at the tournament for the first time since 2015, broke once in the deciding stage of each set to progress into the last 32 against Norway's Casper Ruud.

The 2009 winner hit 35 winners to the 26 Otte managed in his spirited effort, which also saw him earn, and waste, two break points when Federer served out the second set.

"I didn't know his game at all," Federer said in an on-court interview. "It was very complicated. I am very relieved."

He later added: "I think I was just able to keep the pressure on by holding my serves and then with my variety and experience, I guess today it worked well on the big points."

Sixth seed Stefanos Tsitsipas also worked against Bolivia's Hugo Dellien, fighting from 4-2 down in the fourth set in a 4-6, 6-0, 6-3, 7-5 comeback victory.

2015 champion Stan Wawrinka progressed with an impressive 6-1, 6-4, 6-0 against Chile's Cristian Garcin and next meets former top-10 player Grigor Dimitrov, who put out 11th-seeded former U.S. Open champ Marin Cilic, 6-7 (3-7), 6-4, 4-6, 7-6 (7-2), 6-3.

The women's draw, meanwhile, opened when Kiki Bertens, the fourth-seeded 2016 semifinalist and recent Madrid winner, retired sick trailing 3-1 against Slovak Vikoria Kuzmova.

"It's been a great few weeks, and then if you feel like this during a grand slam where you felt good, it's just really annoying," Bertens said.

But 2016 champion Garbine Muguruza, 2018 runner-up Sloane Stephens and second seed Karolina Pliskova posted straight-set wins into round three.

Stephens, the seventh seed, prevailed over Spain's 75th-ranked Sara Sorribes Tormo 6-1, 7-6 (7-3), wasting a 3-0 lead in the second set but then denying her opponent from twice serving out the set at 5-4 and 6-5.