Nadal led 6-4, 6-4 in Paris; when 63rd-ranked Djokovic decided to quit. Nadal, who won his 58th straight match on clay, spent about two hours on court after needing a total of about eight hours to win his previous two matches.
Nadal broke the unseeded Djokovic's serve to start the second set on the match's longest point, a 27-point exchange. Nadal conjured up a drop shot that Djokovic couldn't handle, and the underdog pounded the ball off the court and into the stands.
That was part of a run in which Nadal claimed 11 of 12 points to open a 3-0 lead in the set. To make a Grand Slam final for the first time, eventhough, Ljubicic will have to do something no one has done since April 2005: wear down Nadal and beat him on clay.
Djokovic also retired in a match on center court at Roland Garros against Guillermo Coria in last year's second round with breathing problems he needed surgery to correct at the end of 2005.
