Rafael Nadal ground out a three-set victory over Tomas Berdych to end the Czech's hopes of reaching the semi-finals at the ATP World Tour Finals.
Nadal appeared on course for a routine victory as he came through the first set with something to spare, but Berdych hit back in stunning style to level and looked the more likely winner for spells in the decider.
But the Czech's serve fell apart at a critical juncture allowing Nadal to claim a hard-fought 6-4 1-6 6-3 victory that ensures Stanislas Wawrinka joins the Spaniard in the last four.
Nadal was looking to record a 16th successive win over Berdych and things looked ominous for the number five seed when the Mallorcan broke him in the opening game of the match after he fired a forehand long.
By contrast the Czech made little impact on Nadal's delivery and the one break proved sufficient for the Spaniard to wrap up the set, confirmed when his opponent again blasted long.
But Berdych made a far more positive start to the second as he held to love and, adopting a more attacking mindset, he duly broke the Nadal serve for the first time in the next game when his rival put a forehand wide.
Clearly unsettled, Nadal began to make more unforced errors and quickly found himself a double-break down as Berdych unleashed a powerful forehand winner that clipped the tape.
Nadal managed to avoid the ignominy of suffering a 'bagel' as he held to 15 in the sixth game, but it proved a temporary reprieve as Berdych sent down his 11th ace to wrap up an impressive set in fine style.
The Spaniard was then taken to deuce in the first game of the decider as he battled to stay on terms and it was certainly Berdych who put the opposition serve under more pressure.
However, that all changed in the eighth game as Berdych threw in a double-fault and an error as Nadal brought up three break-points from nowhere.
Although the Czech fended off the first, a second double-fault gifted Nadal the break and from there he served out with little trouble to maintain his winning streak over the Czech - much to the delight of Wawrinka.