Giantkilling Belgian David Goffin is savouring the sweetest success of his career after stunning Roger Federer and the tennis world to surge into the final of the season-ending championships in London.
Backing up his shock group win over world No.1 Rafael Nadal, Goffin ended Federer's year with an improbable 2-6 6-3 6-4 comeback win over the 19-time grand slam champion on Saturday.
After consigning Federer to just his fifth loss of 2017, Goffin will play Bulgarian Grigor Dimitrov in Sunday night's final.
Long touted as Federer's heir apparent, 26-year-old Dimitrov is starting to live up to his rich potential and guaranteed himself the year-end world No.3 ranking with a 4-6 6-0 6-3 victory over American Jack Sock in the second semi-final.
Goffin had lost all six previous meetings with Federer -- and the last eight sets -- heading into their latest encounter.
With Federer cruising through the opening set for the loss of only five points on serve, another hiding looked on the cards.
But the world No.8 raised his game to deny the Swiss superstar a record 10th appearance in the title match and the chance to crown his spectacular comeback year with a seventh World Tour Finals triumph.
"Words can't describe how I'm feeling at the moment. So much joy and happiness," Goffin said after joining Novak Djokovic and Nikolay Davydenko as only the third man to beat both Federer and Nadal at the showpiece season finale.
"It's such a special moment. It's unbelievable. I cannot describe it.
"I was a little bit nervous when I started the match and then I started to feel the ball, the serve was there and it helped me a lot at the end.
"I was a little bit nervous at the end again but I hit some great serves, some great forehands. It was my day."
Dimitrov crushed Goffin 6-0 6-2 in their round-robin match on Wednesday.
"But now it's the finals. It's a different match," Goffin said.
"It's always special to play the finals."
