Stan Wawrinka set up an all-Swiss semi-final with Roger Federer at the ATP World Tour Finals with a 7-6 (7-4) 6-4 triumph over Andy Murray at the O2 Arena.
The pair went into the final Group Ilie Nastasie clash knowing that the victor would book their place in the final four and it was the world number four who appeared to have the greater determination to progress.
In a tight and tricky first set, the two players showed great variation to their games - Murray mixing accuracy with elegance while Wawrinka added finesse to his trademark power.
The world number two attempted to force Wawrinka out into the wide areas, but the Swiss' power saw him edge away, though Murray recovered in order to take the set to a tie-break.
But after leading 4-2, Murray produced costly errors which enabled his opponent to secure five straight points - the last of which came as Murray angled a lob wide.
Wawrinka's backhand was proving impressive, regularly catching Murray short with cross-court efforts in the second set.
Momentum continued to build for Wawrinka and another powerful backhand down the line proved key to breaking Murray and moving 5-2 up.
Murray showed fantastic resolve to win nine of the next 12 points, with individual errors costing Wawrinka as the Briton moved to within one game.
But Wawrinka collected himself and, after saving two break points when serving for the match, saw out a straight-sets victory with Murray leaving the door open for Federer to displace him as world number two at the end of 2015.
Wawrinka  bt Murray 
Murray - 2
Wawrinka - 4
BREAK POINTS WON
FIRST SERVE PERCENTAGE
Murray - 57
Wawrinka - 45
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Murray - 68
Wawrinka - 76