World No.1 Rafael Nadal produced an imperious performance to continue his assault on a maiden ATP World Tour Finals crown by knocking out Roger Federer in straight sets at London's O2 Arena.
Nadal prevailed 7-5 6-3 and will meet either Novak Djokovic or Stanislas Wawrinka in Monday's final.
The 26 year old saved three break-points before breaking Federer's serve twice in the opening set, serving it out at the second time of asking.
The current French and US Open champion then seemingly strolled through the second set without alarm to book his place in his second season ending tour final, and first since 2010.
Six-time winner Federer is however left to reflect upon a year without a major or a customary end of season title for the first time since 2002, though a last four finish, which followed wins over Richard Gasquet and Juan Martin del Potro, represents a late season improvement for the Swiss.
Despite having claimed two grand slam titles, reclaiming world No.1 and possessing a 21-10 win-loss record, Nadal could convincingly be billed as the underdog heading into a 32nd meeting with Federer, after having lost all four of the pair's previous indoor meetings.
The Spaniard was therefore keen to put early pressure on the Federer serve, but such eagerness threatened to have the opposite affect, with the 17-time grand slam champion creating three point chances as early as the sixth game.
Nadal showed the doggedness we've come to expect, producing a spate of forehand winners to save face, and just three games later came the customary sucker-punch.
Federer wobbled after a double-fault at 15-0, netting two on the forehand side before Nadal converted the first of two break points with a brutish blow down the line.
But if the previous 31 meetings between the pair was to be any reflection on their latest joust it was that unpredictability would lie at every turn and though Nadal would serve for the set, Federer would provide the ideal repost.
A stunning exchange ended with a swatted Federer forehand winner and when faced with two more break points, Nadal was powerless to prevent parity being restored.
The back foot though is made for Nadal as he reeled off a second break of the Federer serve without seemingly breaking sweat, as the Swiss netted carelessly to lose the initiative once again.
Normality resumed as Nadal held to love to lead by a set, and after nervous exchanges in the second, the No.1 seed struck unceremoniously, as Federer dumped a withering forehand into the net, to break at 3-2.
Nadal escaped a potential break chance as he benefitted from a net cord serving at 4-3; the last chance that Federer would get as he netted twice before floating a half-volley long to gift his Madrid-born opponent the two-set win inside just 79 minutes.