Sainz -- known as 'Dr Mabuse' after the 1922 film depicting a fake doctor -- was sentenced to two years in prison in 2014, with 20 months suspended, for inciting doping and illegally working as a doctor.

LONDON (AFP) - 

Juan Martin del Potro moved to within one victory of a potential Wimbledon rematch against Novak Djokovic on Tuesday, but would love to find his feet first.

The injury-prone Argentine slipped all over Court Two on Tuesday before he completed a 6-3, 3-6, 7-6 (7/2), 6-4 win over Thanasi Kokkinakis of Australia.

Del Potro's reward is a second round clash against unpredictable Latvian Ernests Gulbis.

If he gets through that, the 28-year-old former US Open champion could face Djokovic four years after he lost to the Serb in the longest semi-final ever played at Wimbledon.

"I know I could face Novak but first I have to win my second round match," he said.

"Everybody knows how good is Ernests on this surface. He has a good day, he can beat all the guys on tour.

"I have to be focused doing my job, doing my serves and forehands. If he give me a little chance to break the serve, I will try to take it."

Del Potro's career, which saw him sweep to the US Open title in 2009, has been plagued by long-standing wrist problems.

They have required three surgeries and pushed him close to retirement last year.

He faced down possible injury fears again on Tuesday as he constantly struggled to stay on his feet before subduing Kokkinakis.

"It's always slippery but you must deal with that. You have to learn the movements on this surface," said 29th seed Del Potro, who needed seven match points to seal his win.

"At the beginning of this tournament, it's complicated to move. But in the end, when the court is dried and the sun comes out, it is much easier to move."

Gulbis, now down at 589 in the world rankings after reaching a high of 10 in 2014 on the back of a shock run to the French Open semi-finals, reached the second round with his first win on the tour in 13 months.

The 28-year-old Latvian brushed past Victor Estrella of Dominica 6-1, 6-1, 6-2 out on Court 16.

Such was Gulbis's routine win that the most dramatic moment came when a ball girl collapsed and had to be escorted off court in a wheelchair.