World number two Novak Djokovic handily beat Stanislas Wawrinka 6-3, 6-3 in the second match of the day at the 02 stadium.
Roger Federer, finishing the worst season in more than a decade, earlier fell to world number one Rafael Nadal, who looked commanding as he defeated his long-time rival 7-5, 6-3.
The results set up a final on Monday between Nadal and defending champion Djokovic as they meet for the sixth time this year.
Wawrinka, ranked eighth and playing in his first World Tour Finals competition, made it easier for Djokovic by committing numerous unforced errors.
By the second set it looked like the Lausanne native was going through the motions toward an inevitable finish, despite a few flashes of brilliance.
Djokovic dominated the match with consistent returns to Wawrinka’s serves.
It was an inglorious exit, but it capped what has been the best season for the Swiss player who has long played in the shadow of compatriot Federer.
Federer, meanwhile, was dogged again in his match against Nadal by lack of consistency and a total of 32 unforced errors.
"I just struggled to stay consistent enough throughout the match, and that's why he deserved to win.” the 32-year-old Basel native said.
“I just couldn’t come up with the shots when I needed them, forehand or serve, moving forward.”
Federer’s disastrous 2013 campaign has given rise to mention of the “R” word, retirement.
But the 17-time Grand Slam winner, who has failed to make the final of any of the four major tournaments this year, is vowing to keep playing.
Federer's annus horribilis
AFP Sports looks at the low points of the Swiss star's worst campaign for over a decade:
January - Loses in Australian Open semifinal to Andy Murray.
February - Beaten in Rotterdam quarterfinals by Julien Benneteau, breaking a run of 28 consecutive last-eight wins against players outside the top 10.
May - Thrashed 6-1, 6-3 by Rafael Nadal in Rome Masters final, sending him into the French Open without a title in the year for the first time since 2000.
June - Crashes out of the French Open quarterfinals in straight sets against Jo-Wilfried Tsonga.
June - Defeats Mikhail Youzhny to win first and only title of 2013 at Halle, Germany and 77th career trophy to tie John McEnroe at number three in Open Era title-winners list.
June - Hits a new low as the defending champion loses to world number 116 Sergiy Stakhovsky in second round at Wimbledon. It is Federer's earliest defeat at Wimbledon since 2002 and his earliest loss at a Grand Slam since losing in the French Open first round in 2003. The result ends Federer's run of 36 consecutive Grand Slam quarter-final appearances.
July - Appearing in Hamburg for first time since 2008, Federer loses to world number 114 Federico Delbonis in quarterfinals. It is just the 12th time in his career he has lost to an opponent outside the top 100.
September - Fails in his bid to reach his 41st Grand Slam quarterfinal when Spain's Tommy Robredo sweeps to a surprise straight sets win in the US Open fourth round.
October - Announces the end of his coaching partnership with Paul Annacone, who had worked with him since July 2010.
November - Suffers 22nd career defeat to Nadal to end year with a loss in the semifinals of the ATP World Tour Finals.