Rafael Nadal suggests end could be in sight if he cannot return to 'high level'

World No 2 has lost in three successive clay court tournament semi-finals and next heads to Rome as defending champion

Rafael Nadal is yet to win a clay court title this season and heads to the Italian Open as the defending champion. Reuters

Rafael Nadal has suggested he could walk away from tennis if he feels he can no longer play at a "high level", although the world No 2 remains confident he can win more titles.

Nadal, 32, crashed out of the Madrid Open semi-finals 6-4, 2-6, 6-3 to Greek world No 9 Stefanos Tsitsipas, which follows last-four defeats in his past two events in Barcelona and Monte Carlo.

The lack of clay court titles, or even final appearances, has raised doubts about Nadal's standing as the dominant force on clay - a status he enjoyed for much of the past 15 years.

"Not winning here means that I'm not going back to my hotel happy," Nadal said after his defeat to Tsitsipas. "But I think I still have tennis ahead of me."

Now Nadal heads to Rome for the Italian Open - where he is the defending and eight-time champion - aiming to win his first clay title before attempting to defend his Roland Garros crown.

Nadal said his longer term focus was on winning a record-extending 12th French Open title.

"In Paris, I have 11 titles. Each week that I play in this tournament is a lot of memories, a lot of unforgettable memories," he said. "What I have to do is to be fit and to play properly and have a high tennis level.

"If I manage to do that ... I think I will still have a very good opportunity to fight for titles for the rest of the year."

After starting slowly on clay last month after another knee injury, Nadal is hopeful of quick progress, but he has alluded to the fact that he could walk away if he cannot return to his best.

"I've done a few steps forward, maybe not enough, but I have improved some things. We'll see (for how long) I can play at a high level - and I think I will be able to continue.

"If I'm not able to do these things properly, that is the end of the situation, period. This is a sport and in a sport it's a matter of winning and sometimes losing and accepting both as naturally as possible."

As in Monte Carlo and Barcelona, Nadal will be defending a title in Rome after beating Alexander Zverev in the 2018 title showdown.

The second seed behind Novak Djokovic opens in the second round against one of two Frenchmen, Richard Gasquet or Jeremy Chardy.

"I've played just three tournaments on clay this year," Nadal said. "It's not much. I play when I want to play and I play where I want to play. I just play for my happiness and I play when I really want to play. That's all."

Kiki Bertens won the Madrid Open on Saturday and will be a leading contender for the French Open. Reuters

While Nadal endures a period of uncertainty, Madrid Open women's champion Kiki Bertens can revel in the biggest title of her career.

Bertens, 27, became the first woman to win the Madrid title - a Premier Mandatory event - without dropping a set after beating Simona Halep 6-4, 6-4 in Saturday's final.

The Dutchwoman will also move up to a career-high No 4 in the world rankings and will be one of the leading contenders at the French Open later this month.

"I just feel really happy. I am really proud of this week. I played some good tennis and will be No 4 in the world on Monday, it is just all amazing things," Bertens said.

For Halep, the defeat meant a missed opportunity to return to the top ranking, but having just returned from injury it was an encouraging run to the final ahead of her French Open title defence.

And the Romanian was gracious in defeat, insisting she was beaten by the better player on the day.

"She played better tennis tonight. She deserved to win the match, definitely," Halep said. "I think I played wrong, and I'm upset about that. I played stupidly today, I did everything that she liked. It was a good match from her. And she deserved to win the title because she played really good tennis throughout the whole week."