Roger Federer moved to within one win of a record sixth year-end crown after beating David Ferrer to reach the final of the ATP World Tour Finals.
The 16-time Grand Slam champion was not at his vintage best but had far too much for Ferrer, winning 7-5 6-3 in an hour and 25 minutes at London's O2 Arena.
He is into his 100th career final and will now leapfrog Britain's Andy Murray to finish the season as world number three - his ninth straight top-three year-end ranking.
In Sunday's showpiece he will play Jo-Wilfried Tsonga, who beat Tomas Berdych 6-3 7-5 in the second semi-final.
"I'm very happy to have played so well again," said Federer. "That's what it takes to beat David. He's had an amazing season and tournament so far."
Federer has now won all 12 of his meetings with Ferrer and he becomes only the third player to reach the year-end championship final seven or more times.
It is his 806th match win, tying him with Stefan Edberg for sixth all-time in the Open era, and his unbeaten run now stands at 16 matches.
Ferrer can be proud of a fine tournament, beating Murray and world number one Novak Djokovic en route to the knockout stage.
The Spaniard will now turn his attention to the Davis Cup final against Argentina from 2-4 December.
He was back in action less than 16 hours after Friday's defeat by Tomas Berdych and there were signs of fatigue as early as game five.
Two languid double-faults left him in a perilous position at 0-30 and despite managing to pull level, a wayward forehand give Federer break point.
However, the Swiss legend twice went long to let his opponent off the hook and that seemed to fill Ferrer with confidence.
He came through his next two service games fairly comfortably and then, at 5-4, picked the perfect moment to go after Federer's delivery.
The crowd murmured nervously as a poor forehand from the fourth seed took game 10 to deuce, and Ferrer prevented him from serving out on a further four occasions.
But the 5ft 9in right-hander was having terrible trouble landing his backhand inside the court and Federer eventually forced his way over the line.
Federer made an uncharacteristically high 19 unforced errors in the first set, but he was quickly into his stride at the start of the second, swiftly raising his first-serve percentage from 55% to 82%.
There was a sense that Ferrer's big chance had been and gone, and so it proved when Federer followed a lob with a stop-dead volley to register two break points.
He took the second of those when Ferrer lashed a forehand wide and then served out to confirm to the delight of his supporters.
"He had the upper hand from the baseline in the first set," Federer reflected. "I was struggling to hit the ball cleanly.
"The hold at 5-5 gave me lot of confidence from the baseline. Looking back, that was the key to the match."
A missed forehand from Ferrer brought up break point in game one, and Federer showed how it was done by landing the same shot for a stunning winner.
The advantage was consolidated with two ultra-cool service holds for 3-1 and then came two chances to secure the double-break.
Three backhand errors and a long forehand kept Ferrer's hopes alive.
But Federer held to love for 5-3 and then attacked his opposite number once more, forcing him to put a forehand wide on match point number two.
In the doubles, Max Mirnyi of Belarus and Daniel Nestor of Canada reached the final by beating American twins Bob and Mike Bryan 7-6 (8-6) 6-4.