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

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

US Open champion and last year's runner-up at Roland Garros Dominic Thiem survived a third-set wobble to beat American qualifier Jack Sock 6-1 6-3 7-6 (10-8) to book his third-round spot.

After No.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 his win-loss record at Roland Garros to 95-2.

After a first-round match played in chilly and damp conditions, the 34-year-old benefited from better weather on Wednesday.

"Today was not that cold, so that's the main thing. Not that cold, the conditions are not that bad," said the Spaniard, who had complained about the new balls used in Paris being too heavy.

"The ball is still heavy. When is not that cold, the ball is little bit less heavy always. I see the predictions the next couple of days are not very good."

That means Nadal may have to play under the closed roof on court Philippe Chatrier for the first time, but he looks in good form.

He fired 17 forehand winners against McDonald, faced zero break points and made only eight unforced errors in a performance that should boost his confidence after he lost in the Italian Open quarter-finals this month to Argentine Diego Schwartzman.

Nadal looks to be on a semi-final collision course with Thiem, whom he beat in the last two finals in Paris.

The Austrian world No.3 needed just 25 minutes to break Sock, a former top 10 player, three times and storm through the first set.

Thiem was brimming with confidence on his favourite surface after winning his first grand slam title earlier this month.

Thiem will next play the winner of the match between in-form Norwegian Casper Ruud, a semi-finalist in Rome this month, and American Tommy Paul.

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 (7-5) 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 past seven anywhere -- the one loss coming in a heartbreaking defeat to Thiem in this month's US Open final.

Australian Associated Press