Stan Wawrinka set up a deciding round-robin encounter with Andy Murray at the ATP World Tour finals by powering to a straight-sets win over David Ferrer.
The French Open champion, beaten by Rafael Nadal in his first match of the season-ending showpiece, fought back from a break down in the first set to win 7-5 6-2.
Wawrinka had cut a frustrated figure as Ferrer played the more disciplined tennis in the first set but the Spaniard surrendered the initiative with some poor serving.
That opened the door for the Swiss to take the first and, from there, Wawrinka was always in the ascendancy as he surged to success.
Having leant on his trademark backhand to emerge triumphant, Wawrinka will now face Murray on Friday with the winner set to join Nadal in the last four.
Ferrer, meanwhile, will be playing for little more than pride when he meets compatriot Nadal, but he appeared poised to take control of the match as he broke first.
An errant Wawrinka backhand handed him a 3-1 lead but, although he saved two break-back points to go 5-2 up - a double-fault when aiming to close out the set put things back on serve.
Another double gave the advantage to Wawrinka, and the fourth seed made no mistake in holding to love to clinch the set.
Wawrinka carried the momentum through to the second by breaking immediately for a 1-0 advantage and he furthered his command in the fifth game with a passing backhand to go 4-1 up.
Ferrer fought back from 30-0 behind at 5-1 down to avoid dropping a fourth straight game and stay alive in the match, but Wawrinka's victory was complete with a forehand down the line.
The shot was ruled in despite hawkeye indicating it was long, with a forlorn Ferrer unable to challenge as his title hopes came to an end.
Wawrinka  bt Ferrer  7-5 6-2
Wawrinka - 3
Ferrer - 0
BREAK POINTS WON
FIRST SERVE PERCENTAGE
Wawrinka - 55
Ferrer - 65
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Wawrinka - 67/76
Ferrer - 61/44
Wawrinka - 74
Ferrer - 59