By Martyn Herman
LONDON (Reuters) - Roger Federer saved four match points before winning a gripping semi-final in a deciding set tiebreak against fellow Swiss Stanislas Wawrinka on Saturday to set up a dream ATP World Tour Final climax with Novak Djokovic.
Six-times champion Federer survived a nerve-shredding battle before emerging victorious 4-6 7-5 7-6(6) in the standout match of the week at London's O2 Arena, although Wawrinka should have prevailed.
Serving at 5-4 in the final set Wawrinka lost his nerve and watched three chances to claim a rare victory against his close friend slip agonizingly by -- the second of which was a feeble volley into the net that will give him nightmares.
As an intense duel moved into the tiebreak both men looked out on their feet. Wawrinka had another match point at 6-5, this time on Federer's serve, but again he could not take it.
Federer then completed a remarkable two hour 48 minute victory in the coolest manner possible, producing a nerveless drop volley to end the contest.
Earlier world number one Djokovic beat Japan's Kei Nishikori, also in three sets.
(Reporting by Martyn Herman; Editing by Ken Ferris)