Rafael Nadal
Nadal's troubles in 2015 continued in Miami.Getty Images

Rafael Nadal's struggles since returning to tennis refuse to abate after the world number three was dumped out of the Miami Open by fellow-Spaniard Fernando Verdasco.

The 28-year-old was humbled 4-6 6-2 3-6 by Verdasco, who faces Juan Monaco in round four, amid a harrowing performance from the 14-time grand slam champion who has reached one major singles final since undergoing surgery in 2014.

Nadal won the Argentina Open in February but suffered a premature exit in Indian Wells and now in Miami, performances which represent a miserable start to 2015 after his quarter-final exit at the Australia Open.

"It's not the question of tennis," said Nadal. "The thing is the question of being relaxed enough to play well on court. One month, or one month and a half ago, I didn't have my game. My game in general has improved since a month and a half.

"At the same time, I'm still playing with too much nerves for a lot of moments, in important moments, still playing with a little bit of anxious[ness]. But I'm gonna fix it. I don't know if in one week, in six months, or in one year, but I'm gonna do it.

"I'm feeling more tired than usual, feeling that I don't have this self-confidence that when I hit the ball, I'm gonna hit the ball where I want to hit the ball, to go for the ball running and knowing that my position will be the right one. All these are small things that are difficult to explain.

"I'm trying to be honest. I am saying the things that I feel today," he said. "But at the same time, I tell you that I have been able to change a lot of negative situations in my career.

"I want to do it again. I'm gonna work to do it again. I am confident that I can do it. I don't know if I'm gonna do it, but I hope I can."