5 storylines to watch at the 2017 French Open

It's been a decidedly strange first half to the 2017 tennis calendar, with all-over-the-map results that have seemed to either turn back the clock or wind it forward. Neither the men's or women's tours have produced much in the way of consistency or predictability.

But the season will ultimately be defined by what happens over the next three months, starting with the French Open, which begins its main draw Sunday. Here are five storylines to keep an eye on as Grand Slam season kicks off at Roland Garros.

All eyes on Novak Djokovic

Despite some recent signs of life, the world No. 2 still doesn't quite look like himself. A year ago at this time, Djokovic looked indestructible, completing his career Grand Slam while capturing his fourth straight major crown. The past 12 months have revealed a more fragile soul. Djokovic has won no Slams and just two tournaments since his historic French Open title, and he responded to his ongoing slump by gutting his coaching team.

In Paris, he'll be working with Andre Agassi, a superstar pairing that's bound to produce plenty of intrigue, whether successful or not. At this point there's little Agassi can illuminate for Djokovic in terms of tactics, but one wonders whether he can't help with the mental side of the game, where Djokovic has seemed to need the most help.

There have been some heartening takeaways for Djokovic from the clay-court season so far, particularly his reminiscently dominant wins over Juan Martin del Potro and Dominic Thiem in Rome. But, as has been the case all year, he tempered the optimism from those matches with a finals performance as disconcerting as the others were encouraging. He continues to struggle with big servers (Nick Kyrgios, Alexander Zverev), and just hasn't been able to string together enough consistency to inspire confidence that he can win seven straight matches to defend his title, even in a best-of-five format that will afford him more opportunity to problem-solve on the fly.

Related: A resurgent Rafael Nadal looks poised to claim his 10th French Open title

Opportunity knocks in wide-open women's draw

For the first time since 2011, a Grand Slam will not feature Serena Williams. In case her absence didn't open up the women's draw enough, Maria Sharapova was also denied a wild-card entry here, while Victoria Azarenka is still on maternity leave for another few weeks.

Defending champ Garbine Muguruza has had a pretty lousy clay season and has been wracked by injuries all year long (four retirements in 10 tournaments), world No. 1 Angelique Kerber hasn't beaten a single top-30 opponent this year, No. 2 seed Karolina Pliskova is a complete non-factor on clay, and just about every contender appears to be carrying some nagging ailment into the tournament. It's hard to remember a major that's been so devoid of favorites, so utterly up for grabs.

Players like Elina Svitolina, Kiki Mladenovic, Anastasia Pavlyuchenkova, and Anett Kontaveit are suddenly in the conversation. The door is wide open, and whether for those who've been knocking on it for a while, or those who've only just arrived to the party, opportunities for a Slam breakthrough won't come much better.

Halep can slay her Grand Slam demons ... ankle permitting

More than anyone, Simona Halep appears to have an opening here; a viable path to a long-awaited first major title. Or at least, she did, before tearing an ankle ligament in the Italian Open final last week. It appears as though she'll still be playing in Paris, but she may be too physically compromised to make the opportunity count.

If her ankle holds up, though, Halep is the closest thing the women's draw has to a favorite. She's probably the best pure clay-courter in the field, and before suffering the injury, she was tearing up the red brick. She made the semis in Stuttgart, won Madrid, and stormed out to a 5-2 lead in the final in Rome when her ankle gave out against Svitolina. She has a straightforward draw, and could get another crack at Svitolina in the quarters.

Halep hasn't made a Slam final since her breakthrough at Roland Garros in 2014. For as good as she's been at other points throughout the past three seasons, she's always faded a bit on the biggest stage, succumbing to physical and mental setbacks in equal measure. In recent weeks, she's looked prepared to rise to the occasion. But movement is her biggest weapon on clay, and if she can't move the way she typically does, it'll likely be another disappointingly early Grand Slam exit for the fourth-ranked Romanian.

Zverev, Thiem ready to take center stage

It's been a long time coming, and after waiting out a wave of disappointing also-rans, we may finally be about to see a player born post-80s win a Grand Slam. Even as the ATP's top five this week is populated entirely by 30-and-older men for the first time in the 40-plus-year history of the computer rankings, the 20-year-old Zverev and 23-year-old Thiem have emerged as fringe French Open contenders.

Zverev is coming off not only the biggest title of his career, but the biggest title for any player his age in over a decade. With his screaming serve and scorched-earth backhand, the undaunted German dismantled Djokovic in the Rome final last week, becoming the youngest player to win a Masters title since Djokovic himself did so in 2007. Much as clay doesn't seem like the surface most conducive to his game, he's proven he can hit through the court against even the game's stoutest defenders. And after debuting in the top 10 this week, he finds himself in arguably the most vulnerable quarter of the Roland Garros draw, headlined by the slumping Andy Murray and perennially hobbled Kei Nishikori.

Thiem is more of a natural clay-courter than Zverev - with similarly destructive groundstrokes that come with far more topspin (if considerably less consistency) - and he made the semis in Paris last year. He eviscerated prohibitive French Open favorite Rafa Nadal last week in Rome with one of the finest baselining displays you'll ever see. Durability remains an issue for the over-scheduled Austrian - he completely ran out of gas against Djokovic in his subsequent match - but at his best, he looks like the heir apparent to Nadal's clay-court dynasty. Win or lose, he'll be one to watch this fortnight.

Kvitova returns

A sight for sore eyes at Roland Garros: Petra Kvitova will be back in action for the first time since being stabbed in the racket hand by a home invader over five months ago.

There won't and shouldn't be any expectations on the two-time Slam champion in her return from the horrific December incident. Some rust seems inevitable, and she's never had much French Open success, anyway. Getting back on the court - a month ahead of schedule, no less - is the real accomplishment. Watching her compete again will be a treat, even if it's just for one match, and anything else would be gravy.

That said, gravy could well be in the offing. Because of her protected ranking, Kvitova comes in seeded 15th, which will give her a couple very beatable early-round opponents. The Czech woman has a chance to make some noise in Week 1.

(Photos courtesy: Action Images)