Suffering a setback on his return from a hip injury in Acapulco hurt Rafael Nadal more than having to retire in the Australian Open quarter-finals.

Nadal pulled out in the fifth set of his last-eight clash against Marin Cilic at Melbourne Park due to the issue, which he aggravated while training ahead of the Mexican Open at the end of February.

The world number one, who helped Spain overcome Germany in the Davis Cup World Group quarter-finals on his comeback last week, said that relapse was more difficult to deal with mentally.

Quizzed on whether he was worried about suffering another setback when he returns to the ATP Tour at the Monte Carlo Masters in the coming week, Nadal said: "Well it happened twice so you never know."

"Being honest, I am not practicing thinking about if that comes back or not. I had injuries in my life, as you know, more than what I expected, but the good thing is that when I came back I was not afraid about what was going on."

"Australia was a tough moment, of course, being in that quarter-final, winning the match and having that problem, having a good chance. But I took the right time to have the right rest. I did all the things that the doctors told me. Then I felt great practicing in Acapulco, playing very well, but then just the day before... I felt it again. So that's the real thing."

"For me mentally the second one was even harder than what happened in Australia, even if Australia was a grand slam and was an opportunity lost. The second one was frustrating because I did all the things the right way."