Rafa Nadal continued his quest for a record-extending 13th French Open title with a 6-1 6-0 6-3 crushing of American Mackenzie McDonald to advance into the third round.

The Spanish second seed, also looking to equal Roger Federer's men's record of 20 singles Grand Slam titles, was never bothered on court Philippe Chatrier.

The claycourt master played deep, used his forehand to devastating effect to set up a meeting with Japanese Kei Nishikori or Italian Stefano Travaglia.

After world number 236 McDonald won the second game, Nadal bagged 11 games in a row to move two sets up and despite some resistance from his opponent early in the third set, he had no trouble improving win-loss record at Roland Garros to 95-2.

Critics have often questioned Alexander Zverev's mental toughness but when it comes to five-set marathons at the French Open the German's fortitude cannot be doubted.

The 23-year-old sixth seed was nowhere near his best against French doubles specialist Pierre-Hugues Herbert but chiselled out a 2-6 6-4 7-6(5) 4-6 6-4 victory.

He has now won all six of his matches that have gone to a deciding fifth set in Paris and six of his last seven anywhere - the one loss coming in a heartbreaking defeat to Dominic Thiem in this month's US Open final.

"I'm pretty fit," Zverev said after battling Herbert for a minute under four hours when asked for the key to his success in fifth-set deciders. "You know, sometimes I just feel like I find a way, like today. Today I was not the better player on court.

"I was not doing anything better than he did. But I found a way, which was the most important. But, yeah, I think I lost the most important five-setter in my career so far, which is upsetting but it's okay."

Zverev will next face Italian Marco Cecchinato who he beat en route to this year's Australian Open semi-final.