Andy Murray missed out on a place in the last four at the ATP World Tour Finals as Stan Wawrinka won their final group match in straight sets.
The Swiss fourth seed came through 7-6 (7-4) 6-4 in London and will play Roger Federer in Saturday's semi-finals.
World number one Novak Djokovic will take on fifth seed Rafael Nadal in the other half of the draw.
Murray heads to Belgium next week for Great Britain's first Davis Cup final since 1978.
Furious Murray bows out
With the remaining semi-final place coming down to a straight contest between Murray and Wawrinka, the 17,000 fans at the O2 Arena settled in for something close to a Grand Slam quarter-final.