Rafael Nadal remains unsure when he will return to action with the French Open looming after being forced to withdraw from the Madrid Open.

The 22-time grand slam champion has been struggling with a left hip issue that contributed to his second-round exit at the Australian Open in January.

Nadal pulled out of the Indian Wells Open and Miami Open, while the troublesome injury has also hampered the start of his favoured clay-court season.

Having withdrawn from the Monte Carlo Masters and Barcelona Open, the Spaniard is still not fit enough to participate in next week's Madrid Open on home soil.

And a concerned Nadal is now facing a race to be fit in time for the French Open, which begins in a little over five weeks' time.

"As you know, I suffered an important injury in Australia of the psoas [muscle]," he said in a video published on social media on Thursday.

"Initially it had to be a six-to-eight-week recovery period and we are now on fourteen. The reality is that the situation is not what we would have expected.

"All medical indications have been followed, but somehow the evolution has not been what they initially told us and we find ourselves in a difficult situation.

"The weeks are passing and I had the illusion of playing in tournaments that are the most important in my career, like Monte Carlo, Barcelona, ​​Madrid, Rome, Roland Garros. 

"For the moment, I have missed Monte Carlo and Barcelona. I will not be able to be in Madrid, unfortunately."

Nadal, who has played just four matches this season, added: "The injury still hasn't healed and I can't work out what I need to to compete. 

"I was training, but now a few days ago we decided to change course a bit, do another treatment and see if things improve to try to get to what comes next.

"I can't give deadlines because if I knew I would tell you but I don't know. This is how things are now."

Nadal won a record-extending 14th French Open title with a straight-sets victory over Casper Ruud in last year's final.