David Goffin produced a majestic display to shock hampered world number one Rafael Nadal in an ATP Finals thriller on Monday.
Goffin had not won a set in his previous two matches against the 16-time grand slam champion, but caused an upset with a 7-6 (7-5) 6-7 (4-7) 6-4 win in Group Pete Sampras.
There were doubts over whether Nadal would be fit for the season-ending event due to a knee injury which forced him to withdraw from the Paris Masters and he winced increasingly as seventh seed Goffin turned on the style in London.
Goffin was thrashed by Novak Djokovic after stepping in to replace the injured Gael Monfils for one round-robin match last year, but rose to the occasion against the top seed after becoming the first Belgian to qualify for the singles in the prestigious tournament.
It remains to be seen if Nadal, who battled like a champion to save four match points in the second set, will be able to continue his quest for a first ATP finals title at the O2 Arena.
-- Tennis TV (@TennisTV) November 13, 2017
It was Goffin who claimed the early advantage, breaking in the third game following a couple of Nadal errors, but he undid the good work by drilling a backhand into the net following a double fault to be pegged back at 3-3.
Goffin broke again to go 6-5 up after unleashing a sublime backhand winner only to once again throw in a couple of double faults to ensure a tie-break would settle the first set.
Both players were nervy in a breaker which the Spaniard led 2-0 before going 5-3 down and it was Goffin who struck first to take the set when his opponent netted a backhand.
Goffin's own backhand was proving to be a potent weapon and Nadal was left startled after the world number eight came up with a breathtaking forehand winner en route to claiming a break which gave him the chance to serve out the match.
Yet another Goffin double fault gave two-time runner-up Nadal a vital break back, but the underdog fizzed another sumptuous backhand winner to earn a first match point.
Nadal dug deep to hold and was clenching his fist after saving another three match points from 0-40 in his next service game, going on to raise his game in the tie-break on this occasion after Goffin double-faulted again at a key moment.
The favourite's knee was clearly causing him problems in the final set and he was punished for too many errors, one of which put Goffin a double-break up at 4-1.
Nadal hung in there and broke back, but Goffin marched on and finally put the Mallorca native out of his misery with a 14th ace.
Goffin  bt Nadal  7-6 (7-5) 6-7 (4-7) 6-4
Goffin - 39/43
Nadal - 27/42
Goffin - 14/7
Nadal - 2/2
BREAK POINTS WON
Goffin - 5/13
Nadal - 4/4
FIRST SERVE PERCENTAGE
Goffin - 64
Nadal - 65
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Goffin - 75/54
Nadal - 66/46
Goffin - 113
Nadal - 100