French Open: Novak Djokovic, Zverev 'Only Two' Who Can Beat Rafael Nadal

Novak Djokovic and Alexander Zverev are the only two players capable of preventing Rafael Nadal from winning an 11th French Open crown, according to former Wimbledon champion Richard Krajicek.

Nadal begins his French Open campaign Monday when he takes on Italy's Simone Bolelli as he looks to win his fourth clay title of the year and remain No. 1 in the rankings above Roger Federer.

While he did lose to Dominic Thiem in the quarterfinals of the Madrid Open — the only player to defeat him on clay last year as well — the Spaniard has been otherwise dominant on his preferred clay surface. However, his most recent displays in the Rome Masters showed he could be challenged by other players.

Djokovic, who appears to be getting closer to his best, enjoyed a very competitive first set against Nadal during their Rome semi-final encounter even though he would go on to lose in straight sets.

Then in the final, Zverev almost looked like he would upset the 31-year-old as in the third and final set, he was leading 3-1 only for Nadal to eventually come back and win following a lengthy rain delay.

"Two weeks ago, I was totally convinced that Nadal would win the French Open for the 11th time," Krajicek said, as per Tennis World USA. "But now it seems that two men could seriously threaten him. The first is Alexander Zverev, the German is very solid as the world No. 3 and who won three Masters 1000 titles. In the Rome Open final, he was going to win his fourth, but Nadal's experience was a decisive factor. Zverev is getting close to the big leaders' level, (Roger) Federer and Nadal."

"In the meantime, I see that Novak Djokovic is slowly, but definitely improving. I think that the French Open is coming too early for him, but he is a dangerous outsider. Zverev and Djokovic are the only two men that can keep Nadal off the title in Paris."

Djokovic is one of the few players with a decent record against Nadal on clay as the Serbian has won seven times on 22 occasions, including his most impressive win in their 2015 French Open quarterfinal clash.

And while Zverev is yet to really perform in a Grand Slam, having not passed the fourth round stage, the young German has enjoyed a fine run of form since the start of 2017 with a total of seven titles so far with his most recent triumph coming in the Madrid Open earlier this month.

Zverev kicked off his French Open campaign Sunday, beating Lithuania's Ricardas Berankis in straight sets. Meanwhile, David Goffin survived a scare as he came back from two sets down to defeat Robin Haase.

Grigor Dimitrov defeated Egypt's Mohammed Safwat in straight sets while Kei Nishikori emerged victorious in straight sets as well against Frenchman Maxime Janvier.

Djokovic will begin his Roland Garros campaign Monday against Brazil's Rogerio Dutra Silva and along with Zverev, could face Nadal in the final should they progress that far.