Third seed Rafael Nadal began his bid for a 21st Grand Slam men's singles title with a straight-set win against Australia's Alexei Popyrin.

The 34-year-old Spaniard, going for a record-extending 14th triumph at Roland Garros, won 6-3 6-2 7-6 (7-3).

Serbian top seed Novak Djokovic also eased through to round two, beating American Tennys Sandgren 6-2 6-4 6-2.

Russian seventh seed Andrey Rublev is out after losing in five sets to German world number 42 Jan-Lennard Struff.

Rublev's defeat means there is one fewer obstacle for Nadal in his side of the draw as the Spaniard seeks to set an outright record for major men's singles titles - a milestone he shares with Roger Federer at present.

The Russian was the highest seed behind Nadal in their quarter, with the pair projected to meet in the last eight.

With the seedings based on the world rankings, Nadal is third behind Djokovic and Daniil Medvedev this year and has been landed with a potentially tricky draw.

For the first time, Nadal has found himself in the same half of the draw as Djokovic and Switzerland's Federer, who looked impressive on his return to Grand Slam tennis after a 16-month injury lay-off.

"I am here to try my best, and when you are the third seed, you know that you're going to have the chance to be in the same part of the draw as the number one or the number two," said Nadal.

"This time I was in the part of the draw with the number one. But there still remains a lot for me to do before thinking about the semi-finals.

"I have won my first match, something that I'm happy with and I'm focused on the second one. That's it. The other stuff doesn't worry me much now."