Rafael Nadal says the back injury that struck six weeks ago as he lost the Australian Open final is still not quite right.

The Spanish top seed began his title defence at the Indian Wells Masters as he struggled to beat Radek Stepanek 2-6, 6-4, 7-5 to reach the third round.

“I was a little bit scared for the back, I’m not yet feeling 100 per cent confident with my serve,” said Nadal, who took time off after his Melbourne loss to Stanislas Wawrinka but came back to win a clay title in Rio last month.

“My back is better than Rio, there I was feeling the back not very well. I’m feeling it better now. This match helped me understand my serving limitations. I had no confidence because I was scared to feel the back again.”

Nadal blamed his tentative play for making life tough in his two-and-a half-hour win over Stepanek.

“At the end I give him a little bit of advantage because with my serve I was doing nothing.

When that happens, the opponent can play more aggressive, play more confidence, and with eight double faults I give him opportunity to win a lot of free points.

“I think I can try to serve again at 100 per cent because I am feeling better. The match shows me that I can try,” added Nadal.

The 13-time grand slam winner who took a Mexican holiday last week, said during that time he also took treatment and did not serve for 10 days.