Novak Djokovic admits he knows absolutely nothing about Daniel Galan, the world number 153 from Colombia who stands in his way of a place in the last 16 at Roland Garros on Saturday.

That may be just as well as Galan, a 24-year-old lucky loser from qualifying, says he's not a "diehard follower" of the world number one.

"I don't know much about him, to be honest," said Djokovic, the 2016 French Open champion who is chasing an 18th Grand Slam title. "I have never seen him play, so I'll have to obviously look at his matches, the videos, and try to prepare myself with my team."

Djokovic, whose 2020 record now stands at 33 wins against just one loss, is bidding to become the first man in half a century to win all four Slams twice. His second round win over Ricardas Berankis was his 70th at the tournament. The 33-year-old has now won at least 70 matches at all the majors.

By contrast, Galan's only two wins at the Slams have come in Paris this week. "As a child I grew up with the rivalry between (Roger) Federer and (Marat) Safin," said Galan. "When I was older I admired (Rafael) Nadal for what he has achieved."

Galan was one of nine players outside the top 100 to have reached the third round, the most in Paris since 1985. "Djokovic has no weaknesses, although I am not saying that he is invincible, otherwise he would never have lost a match," added Galan, the first Colombian to reach the third round of a major since Santiago Giraldo in Paris in 2012.

On the day after world number 239 Hugo Gaston and Sebastian Korda, ranked at 213, made the last 16, German qualifier Daniel Altmaier struck another blow for the underdog. The world number 186 stunned seventh seed Matteo Berrettini of Italy 6-2, 7-6 (7/5), 6-4, becoming just the fourth man to reach the round of 16 on his Grand Slam debut since 2000.

Victory also means an unexpected financial windfall for the German who is guaranteed to make at least $221,400 by reaching the last 16 having earned $173,600 in his entire six-year career.

Injured before Paris'

"I didn't know if I was going to be able to play in Paris as I was injured the week before at a tournament in Aix," said Altmaier who had previously only won one ATP Tour match in his career. "But the doctor gave me the go-ahead so I am super-pleased to be here. The tournament continues for me and I am happy to keep going."

Russian 13th seed Andrey Rublev, the champion on clay in Hamburg on the eve of Roland Garros, eased past veteran South African Kevin Anderson in just 94 minutes. Rublev didn't face a break point in his 6-3, 6-2, 6-3 win as he moved into the last 16 for the first time.

Greek fifth seed Stefanos Tsitsipas bids to make the fourth round for a second successive year. He faces Slovenia's Aljaz Bedene, the world number 56. Tsitsipas had to come back from two sets down to defeat Jaume Munar in the first round but then swept past Uruguayan clay court specialist Pablo Cuevas for the loss of just seven games.

In the women's draw, 2017 champion Jelena Ostapenko, who knocked out second seed Karolina Pliskova on Thursday, takes on Spain's Paula Badosa. The New York-born Badosa, ranked 87, is making her Roland Garros debut and marked the occasion by stunning former US Open champion and 2018 Roland Garros finalist Sloane Stephens in the second round.

Australian Open champion and fourth seed Sofia Kenin is up against Romanian qualifier Irina Bara, ranked at 142. Kenin stunned Serena Williams at the same stage of last year's tournament. Spain's Garbine Muguruza, the 2016 champion in Paris and seeded 11 this year, plays Danielle Collins of the United States who is enjoying her best run at the tournament.

French wildcard Clara Burel, just 19 and ranked a lowly 357, faces experienced Chinese player Zhang Shuai who is attempting to become the first Chinese woman in the second week since former champion Li Na in 2012. Two-time Wimbledon winner Petra Kvitova, seeded seven, meets Leylah Fernandez for a last-16 spot.

The 100th-ranked Fernandez, just 18, won the girls' title in Paris last year and is now making waves on her main draw debut after taking down 31st seed Magda Linette and 47th-ranked Polona Hercog.