PARIS (REUTERS) - Novak Djokovic eventually wore down mercurial Latvian Ernests Gulbis 6-3, 6-3, 3-6, 6-3 in tennis' French Open semi-finals on Friday but only after suffering a sudden loss of form in the process.
The Serbian world No. 2 was cruising at two sets ahead but his level dipped suddenly, allowing Gulbis to make a real match of it before he managed to finish the job and remain on course for the only Grand Slam title to elude him.
Djokovic was overpowered by Gulbis in the third set and seemed to be lacking energy but some errors by his opponent in the fourth spared him being dragged into a decider.
The No. 2 seed displayed ice cool efficiency in the first two sets, more consistent from the baseline and clinical when the chances arose in the pair's first match since 2011.
But moments of casual brilliance from 18th seed Gulbis stunned Djokovic in the third which he sealed with an ace after breaking the serve of his worried-looking opponent.
Suddenly what had looked like a straightforward afternoon on Phillipe Chatrier court for Djokovic, last year's runner-up, threatened to turn ugly.
However, he upped his level in the fourth as Gulbis started to wilt, earning the right to take on king of clay Rafa Nadal or Wimbledon champion Andy Murray in Sunday's final.
Gulbis, who had reached the last four of a Grand Slam for the first time after 27 attempts, mostly matched Djokovic's athleticism scrambling around the court but neither appeared to really hit top gear on the hottest day of the tournament.
Djokovic will have to draw deeper on his stamina, belief and weapons if he meets Nadal, who is looking for his ninth title on the Paris clay.
Reaching Sunday's clash mean's Djokovic becomes just the sixth man since tennis turned professional in 1968 to reach multiple finals in each Grand Slam.
Djokovic will reclaim the world No. 1 spot if Nadal fails to win the title.