Second seed Karolina Pliskova ended Mayar Sherif's fairytale Grand Slam breakthrough to set up a Roland Garros second round clash against former champion Jelena Ostapenko on Tuesday as world number one Novak Djokovic pledged to be on his best behaviour on his return to the majors after his US Open brain fade.

Pliskova, a semi-finalist in 2017, squandered eight set points in the opening set as world number 172 Sherif, the first Egyptian woman to play in the main draw at a Slam, took a shock lead.

However, the Czech's greater experience eventually told as she recovered to progress 6-7 (9/11), 6-2, 6-4.

Latvia's Ostapenko, the world 43, won her first match at the French Open since sweeping to her shock 2017 title when she fired 46 winners past Madison Brengle of the United States to win 6-2, 6-1.

Later Tuesday, Djokovic begins his bid for a second French Open title and 18th Grand Slam title.

The world number one tackles Sweden's Mikael Ymer, ranked 80, seeking a 32nd win in 33 matches in 2020.

His only loss was against himself following his now infamous default in New York for an angry swipe of the ball which hit a line judge in the throat.

"Of course, I will make sure I don't make the same mistake twice," said the Serb who remains only one of two men to have defeated 12-time champion Rafael Nadal in 15 years in Paris.

Djokovic suffered no hangover from his US Open controversy, quickly wrapping up a record 36th Masters title in Rome in a perfect claycourt tune-up for Paris.

Eyes front: Karolina Pliskova returns the ball to Egypt's Mayar Sherif
Eyes front: Karolina Pliskova returns the ball to Egypt's Mayar Sherif AFP / Thomas SAMSON

An extra incentive in Paris for the Serb is the opportunity to become the first man in the Open era -- and only the third man in history -- to win each of the four Grand Slam titles twice.

Ymer, 22, who is of Ethiopian descent, hasn't won a main draw match on tour since the sport resumed after its lengthy suspension due to the coronavirus.

However, he made the second round of Roland Garros on his Grand Slam debut last year having come through qualifying before losing to Germany's Alexander Zverev.

Also on Tuesday, newly-crowned Hamburg champion Andrey Rublev, seeded 13, tackles giant American Sam Querrey.

The 22-year-old Rublev's final win in Germany over Stefanos Tsitsipas was his third title of 2020, after hardcourt trophies on Doha and Adelaide.

Rublev has yet to win a match at Roland Garros in two visits following a loss in qualifying in 2016 and a first round exit in 2017.

World 48 Querrey made the third round in Paris in 2013.

Canada's Denis Shapovalov, seeded nine, faces French veteran Gilles Simon.

The left-hander leapt into the top 10 for the first time earlier this month and made the quarter-finals of the US Open and last eight in Rome.

However, Shapovalov, 21, has just one career win at Roland Garros.