(CNN) -- Defending champion Rafael Nadal struggled with a misfiring service and an awkward opponent in veteran Czech Radek Stepanek before battling into the third round of the Masters 1000 event at Indian Wells.
Nadal was in deep trouble in the third and deciding set before pulling out a 2-6 6-3 7-5 victory.
The world number one admitted that the back problem which affected him during his Australian Open final defeat to Stanislas Wawrinka was still leaving him with doubts.
"I was a little bit scared for the back. I am not yet 100 per cent confident with my service," he told gathered reporters after serving eight double faults in the two hour 40 minute encounter.
Stepanek, 35, also posed an unusual challenge as Nadal acknowledged: "He is not the right player to play against in the first match because what you want to find is rhythm and against him every point is different."
Stepanek swept through the first set before Nadal hit back to level and take a break lead in the third set.
Stepanek broke back then forced three break points on the Spaniard's service in the sixth game.
"It's true that with love-40, I was very close to losing, to being out, but I think I did two good serves and then I played a great point," said Nadal.
"Tough one. Anything can happen, but in the end I played well. After that, I think I played better."
The victory extended Nadal's record to 41-6 at the Californian event, which he has won in 2007, 2009 and 2013.
Earlier, third seed Wawrinka came through his first match on the ATP Tour since his triumph in Melbourne, dispatching giant Croatian Ivo Karlovic, 6-3 7-5 without any major drama. "I was a little bit scared about the way I was going to play," said the Swiss, who took time off after his grand slam success.
Roger Federer, who is playing in the doubles with Wawrinka, continued his winning run with a 6-2 7-5 victory over France's Paul-Henri Mathieu.
The 17-time grand slam winner is fresh off his success in Dubai, where he beat world number two Novak Djokovic on the way to the title.
Britain's Andy Murray joined the other big guns in the third round with a three set victory, 4-6 6-3 6-2 over Lukas Rosol, but Australia's Lleyton Hewitt is out, beaten 7-6 7-5 by in-form 17th seed Kevin Anderson of South Africa.
In the WTA tournament at the same venue, top seed Li Na beat Chinese compatriot Zheng Jie 6-1 7-5, while Maria Sharapova returned to tour after her Olympic duties in Sochi with a 6-1 6-4 dismissal of Germany's Julia Goerges.