London - Roger Federer has set up a final showdown with Novak Djokovic in sensational fashion as the Swiss great saved four match points before defeating Stan Wawrinka, 4-6, 7-5, 7-6 (8/6) in a thrilling semi-final at the ATP Tour Finals on Saturday.
Federer looked down and out when Wawrinka served for the match in the final set, but the six-time champion responded superbly and eventually booked his ninth appearance in the final of the season-ending event at London's O2 Arena.
The 33-year-old held his nerve impressively despite an erratic performance in the best match of a tournament sorely lacking memorable encounters this year.
Federer has now saved 11 match points in three winning causes this year, with the others against Gael Monfils at the US Open and Leonardo Mayer at the Shanghai Masters.
The 124th final of Federer's illustrious career is a rematch of this year's Wimbledon final, which Djokovic won in five sets.
Federer has met his great rival on 36 occasions, winning 19 times, but the world number one has won their last three finals, including at the Tour Finals in 2012.
"I think I got lucky tonight. Stan played better from the baseline and that usually does the job on this court. But I kept fighting," Federer said.
"It's tough but I'm thrilled to be in another final in London.
"Novak is playing great tennis. It usually brings the best out of me, it's going to be tough but I'll give it a shot."