Roger Federer and Novak Djokovic will go head to head for the 26th time in the French Open semifinals on Friday and both agreed the outcome lay in the lap of the gods.

At one stage in Tuesday's quarterfinals at Roland Garros it looked like both were on their way out. Federer was two sets to love down against Juan Martin del Potro and at the same time, Djokovic was being run ragged by Jo-Wilfried Tsonga. But, in keeping with their superstar status, both men found a way back, winning in five sets in each case.

Djokovic was on the brink of defeat but dug deep to complete a 6-1 5-7 5-7 7-6 (8-6) 6-1 win in more than four hours.

The 16-time Grand Slam champion, seeded third, overcame Argentina's Juan Martin del Potro 3-6 6-7 6-2 6-0 6-3.