5 storylines to watch at French Open

The tennis world descends on Paris for the second Grand Slam of the season. Will a familiar face add a French Open title to their trophy cabinet or is a rising star ready to stake their claim and hoist the championship trophy on Court Philippe Chatrier?

Here are five storylines to watch when the actions kicks off Sunday.

Rafa seeks 12th French Open

There's a reason why Rafael Nadal is known as the King of Clay. He has an Open era-record 58 clay-court titles, including 11 at Roland Garros, where he's 86-2 all time. Nadal has also historically dominated the schedule leading up to tennis' second Grand Slam. He's won the Monte-Carlo Masters and Barcelona Open 11 times each, the Rome Masters on nine occasions, and owns five Madrid Open titles - all of which are tournament records.

But Nadal - compared to his lofty standards - slumped during this year's clay season. The 32-year-old arrived at the Madrid Open without winning a title at the first two major stops - Monte Carlo and Barcelona - for the first time since 2015. Nadal proceeded to reach the semifinals in the Spanish capital, where he fell to rising Greek star Stefanos Tsitsipas in a three-set battle.

The 17-time major winner is more vulnerable entering the French Open than in years past, but there's no question he remains the favorite. Nadal is riding the momentum of his first clay-court title of the season at the Rome Masters. The Spaniard looked sharp throughout the tournament - dropping just one set - as he avenged his loss to Tsitsipas in the semifinals and took out rival Novak Djokovic in the final. While much was made about his recent results, Nadal won an ATP-leading 42.5 percent of return games during the clay-court season. He'll be able to ease into the tournament with his first two opponents being qualifiers.

Osaka faces challengers for No. 1 ranking

Naomi Osaka has shifted from the hunter to the hunted in a matter of months. The Japanese star claimed her first Grand Slam at the US Open in September 2018 before seizing the world No. 1 ranking after her Australian Open triumph. She now goes into Roland Garros gunning for her third straight major title after entering the French Open ranked just outside the WTA's top 20 a year ago.

Osaka has only 130 points to defend following a third-round defeat to Madison Keys in last year's tournament. While her power game is more suited to hard courts, she's shown improved footwork on clay. The 21-year-old is having her best season on the surface, notching an 8-3 record en route to one semifinal and a pair of quarterfinal appearances.

But an early exit could open the doors for a slew of Osaka's peers to overtake her for the top ranking. Karolina Pliskova captured the Italian Open on Sunday and is just two years removed from a French Open semifinal run. Meanwhile, Simona Halep's counter-punching style led her to last year's title and two other finals appearances. Kiki Bertens, Angelique Kerber, and Petra Kvitova are also threats to the 21-year-old's throne. The draw didn't do Osaka any favors either, with her potential second-round opponent being either 2017 French Open champion Jelena Ostapenko or two-time Grand Slam singles winner Victoria Azarenka.

Federer returns to Roland Garros

After a three-year hiatus, Roger Federer is set to pursue his second career French Open title. A back injury forced him to withdraw from the 2016 tournament and he's skipped the last two clay-court seasons entirely in order to preserve his body.

While just one of Federer's record 20 Grand Slams has come at Roland Garros, he's made the finals on four other occasions, only to fall short against the King of Clay. Federer's 11 career titles on clay are tied for third in the ATP among active players, while his 218 career wins rank fourth. The Swiss Maestro went 4-1 in a pair of recent warmup tournaments that featured impressive wins against top-20 players Gael Monfils and Borna Coric and held two match points before falling to Dominic Thiem, last year's French Open runner-up.

The 37-year-old has little pressure to win and should be playing loose, especially with no points to defend.

"I won here 10 years ago," Federer said of his 2009 French Open triumph, according to the ATP. "It has been one of the greatest moments in my life, so I don't know what to expect as far as the results are concerned. It's a bit like in Australia in 2017. I had no expectations. I'm just happy to be back in good health."

Federer claimed the title that year in Melbourne. But for history to repeat itself, he might have to get by Tsitsitpas and Nadal in potential quarterfinal and semifinal showdowns, respectively.

ATP Next Gen stars look for 1st major

Speaking of Tsitsipas, he leads the ATP's Next Gen stars - players aged 21-and-under - primed to challenge the old guard. The former top-ranked junior player has continually performed on the big stage throughout his young career and is the best bet among the up-and-comers to win their first career Grand Slam at Roland Garros.

In January, Tsitsipas defeated Roger Federer in the fourth round of the Australian Open en route to his first major semifinal. Months later, he advanced to his second career Masters 1000 final after defeating Nadal in the Madrid Open semis. While Tsitsipas' all-around game doesn't suit one surface more than the other, he grew up crafting his game on the clay courts and plays with a comfort that most players have difficulties adjusting to.

His junior rivals - Felix Auger-Aliassime and Denis Shapovalov - also have the potential to make some noise. Both were members of Canada's junior Davis Cup-winning team in 2015, which took place on clay. Auger-Aliassime's athleticism and excellent lateral movement are weapons on the surface. The Montreal native's three ATP challenger titles and his first two career ATP final appearances have all come on clay.

Shapovalov hasn't had much success on the surface outside of a semifinal appearance at last year's Madrid Open. His shotmaking can be erratic at times, but if he can harness that aggressiveness and focus more on constructing points, Shapovalov could be a dangerous draw.

Serena enters with low expectations

It's not often that a 23-time Grand Slam singles champion enters a major as an underdog, but Serena Williams is just that. Injuries have forced her to either retire or withdraw from three of the four tournaments she's played in this year. Williams' lack of match play is concerning, as it requires some time to get accustomed to sliding on clay and the longer rallies on the surface will put her endurance to the test.

"We just don't know her physical status at this point," 18-time major champion Chris Evert told Howard Fendrich of The Associated Press. "She relies so much on the physicality of her game and her movement and her sprinting and just her court coverage and setting up those big shots.

"Her legs are vital to her game. I don't know if we've seen her 100 percent since the beginning of the year."

Williams' draw is loaded with obstacles. Rising star Bianca Andreescu could be a tricky opponent in the third round due to the variety in her game. World No. 8 Ashleigh Barty - who went the distance in last year's Roland Garros meeting against Williams - potentially awaits in the Round of 16. If everything goes according to plan, Williams is set up for a meeting with Osaka in the quarterfinal, their first matchup since the latter's maiden Grand Slam at the 2018 US Open.

Having said all that, the 37-year-old has won three French Open titles and if she didn't have enough motivation already, another crown would tie her with Margaret Court for the women's all-time record of 24 Grand Slam singles titles. Like Federer, the American star isn't known for her prowess on clay, but she owns a 108-30 (.782) mark on the surface, the second-highest in WTA history. It would be a mistake to write off her title hopes.