Roger Federer continues his first Roland Garros campaign since 2015 with a second-round clash against German lucky loser Oscar Otte on Wednesday, while reigning champion Rafael Nadal takes on qualifier Yannick Maden.

Here, AFP Sport takes a look at three matches to watch on the fourth day of the French Open:

Roger Federer vs Oscar Otte

First meeting

Federer cruised through his opening match against Lorenzo Sonego on Sunday, and the 20-time Grand Slam champion is back on Court Philippe Chatrier to take on Otte.

The 37-year-old won his only Roland Garros title in 2009 and is considered an outsider for the tournament this year, but will be a red-hot favourite against the world number 144 Otte – who claimed his first-ever Grand Slam match win against Malek Jaziri in round one.

Federer may not be the same force on clay as he is on quicker courts, but has still been in decent form, reaching the Madrid and Rome quarter-finals.

“I would be surprised if Roger knew my name,” admitted Otte.

Rafael Nadal vs Yannick Maden

First meeting

Nadal started his bid for a record-breaking 12th French Open title with a straightforward victory over German qualifier Yannick Hanfmann – and now finds himself facing another German qualifier named Yannick in world number 114 Maden.

The Spaniard, who is just three behind Federer on the all-time list of Grand Slam titles with 17, has an incredible 87-2 win-loss record at Roland Garros.

Maden, 29, played college tennis in the United States, and like Otte, had yet to register a win at the Slams until this tournament.

“With YouTube you can find things,” said Nadal of the potential pitfalls of facing the relative unknown of Maden.

Nadal will, however, be playing a rare match on Roland Garros’ second arena – Court Suzanne Lenglen.

Elina Svitolina vs Kateryna Kozlova

Svitolina leads head-to-head 1-0

Ukrainian ninth seed Svitolina will have little unknown to face when she takes on childhood rival and 67th-ranked compatriot Kateryna Kozlova.

“I’ve known Kateryna for a long time. We played, I think, when we were eight the first time,” said Svitolina. “I haven’t seen much of her game recently, but we’ll see how it goes.”

Ranked as high as three in the world in 2017, Svitolina has struggled slightly to make a serious impact at the major tournaments and has never reached a Grand Slam semi-final. She is, however, a two-time Roland Garros quarter-finalist.

Svitolina won the pair’s only previous professional meeting in a second-tier event in Donetsk six years ago.