David Goffin on Saturday mounted a spirited fightback to stun six-time champion Roger Federer and reach the final of the season-ending ATP Finals in London.
The Belgian seventh seed, 26, came from a set down to win 2-6 6-3 6-4, his first victory in seven attempts against the 19-time Grand Slam champion.
"I have no words. I cannot describe how I'm feeling - so much joy, so much happiness," said Goffin.
Goffin will face Bulgarian Grigor Dimitrov in Sunday's final, according to a BBC report.
The sixth seed came through 4-6 6-0 6-3 against American eighth seed Jack Sock in the second semi-final.
Dimitrov, 26, will play Goffin for the second time this week, having thrashed the Belgian 6-0 6-2 in the group stage on Wednesday.
"It's another match - I just need to keep on playing," said Dimitrov. "It's the last match of the season so, full house, and we're on."