The Mutua Madrid Open, one of the final clay court tennis tournaments before Roland Garros, is underway.

Simona Halep and Rafael Nadal enter as the odds-on favorites and both have successful career runs in Madrid. Fans of tennis betting want to know: Will each claim another Madrid Open title?

Halep Faces Depth

It will be difficult for either favorite to win out, especially Halep, who sees a much deeper pool of talent.

The Romanian enters Madrid with odds set at +450 to win. Not bad odds considering Halep has won this event twice.

Halep won this event in back-to-back years, 2016-17. Not to mention she has been to a total of three Mutua Madrid Open final appearances.

The WTA is not very top heavy, however, and many other women can challenge Halep for the Madrid crown.

Kvitova is a Contender

Petra Kvitova thrives on a clay court surface. In fact, after Monday’s first-round victory she has won 19 of her past 20 matches on clay.

She faced Kiki Mladenovic and won 6-3, 7-6 (7-5) in the first round, so it was a tough tournament right out of the gate for Kvitova.

The Czech star is used to Madrid, though. Kvitova is the defending champion, having beaten Kiki Bertens (+1600) in last year’s final.

Kvitova’s win last year marked her third title in Madrid, and her odds to win it this year are at +800.

Only Halep and Naomi Osaka (+700) have better odds, as Halep or Kvitova have been the only two women to win Madrid the past four years.

Sloane Stephens has odds to win set at +1600. She defeated Victoria Azarenka in three sets to kick off her tournament on Monday.

Will Nadal Win Madrid?

One would like to believe that Rafael Nadal is a lock to win this tournament, which he should be.

Nadal has won the Mutua Madrid Open five times, the most ever, and enters with odds to win at +135.

The issue with Nadal is both his health and his recent results on clay.

He lost to Dominic Thiem in the Barcelona Open, a tournament Nadal historically dominates. Nadal also lost to Fabio Fognini in the Monte-Carlo Masters.

The former isn't a concern, as Thiem is one of just a handful of people to beat Nadal on clay multiple times in the past few years. Fognini’s loss is a bit more concerning, as Fognini’s clay-court record is nothing to get excited over.

Despite the two losses and injury concerns clouding Nadal this season, he may still be the safe bet with his current odds.

Who Can Dethrone Nadal?

Last year’s champion Alexander Zverev has struggled this season as well, looking impressive in Munich until a sudden loss to Christian Garin.

Zverev has the fourth-best odds to win at +1400, behind both Thiem and Novak Djokovic.

Thiem is an intriguing option at +700, as the Austrian star has reached back-to-back Madrid Open finals in the past two years.

He is on a five-match winning streak but must now face a tough server in Reilly Opelka.

The best value bet, however, is Roger Federer at +2300.

Though he has showing little conviction in Madrid, it’s hard not to consider betting on the greatest tennis player ever.

Federer is coming off a title victory in Miami, where he beat John Isner. Federer’s most recent loss came to none other than Thiem.

Picking between Federer and Thiem may not be a bad value pick for those looking to steer away from the favorites.