Belgium's David Goffin pulled off a huge shock to beat six-times champion Roger Federer 2-6 6-3 6-4 in the semi-finals of the ATP Finals in London on Saturday.
Few gave the willowy world number eight a prayer against the Swiss favourite, especially having lost all six previous meetings, but he staged a remarkable comeback after being outclassed in the first set.
Federer, the world number two, snaffled the opener in 33 one-sided minutes as he feasted on Goffin's steady medium-pace game.
But Goffin broke serve with a forehand winner in the second game of the second set and consolidated his advantage to take the match into a decider.
Growing in confidence the 26-year-old Goffin broke Federer's serve again at 1-1 in the third set as the Swiss, suddenly anxious and struggling for timing, struck a backhand out.
There still seemed plenty of time for 19-times grand slam champion Federer to re-assert his authority but Goffin stayed cool and his moment of truth arrived at 5-4 when he stepped up to serve for the biggest win of his career.
Consecutive aces gave him a 30-0 lead before he buried a nervy forehand in the net. Federer then went wide with a forehand to give Goffin two match points and a swinging first serve proved too good.
First-time qualifier Goffin, nor the capacity O2 Arena crowd, could believe it as the Belgian ensured there will be a new name on the trophy this year.
Fellow debutants Grigor Dimitrov and Jack Sock contest the second semi-final later on Saturday.