But the seventh seed, who 24 hours earlier admitted he did not have a clue how to beat Federer, hit back early in the second set to break and, rejuvenated, knocked his illustrious opponent out of his rhythm. Federer, suddenly looking vulnerable and unable to dominate, was powerless to stem the tide as Goffin went on to level the match before breaking again early in the decider. "I started to feel the ball better at the end of the first set, so I wanted to be more aggressive," said Goffin. "As soon as I had the chance to go for the shot from the return and from the serve, (that) was the key, to go for the shot." Goffin is only the sixth player ever to beat Rafael Nadal and Federer in the same tournament and the first since Novak Djokovic at the 2015 ATP Finals.A moment @David__Goffin will never forget…
— Tennis TV (@TennisTV) November 18, 2017
Roger Federer: defeated. #NittoATPFinals pic.twitter.com/XPCLt1e8Gy
The Belgian, who beat Nadal in his round-robin opener, described his victory against six-time champion Federer as the best of his career. "Both are really special," he said. "It was the first time against Rafa. Then the semi-final for the first time for me here, and to beat Roger for the first time here in such a big event, big tournament, it was the perfect moment. Yeah, it is the best win of my career, for sure." A disappointed Federer missed out on the chance to apply a final flourish to a brilliant season in which he won the Australian Open and a record eighth Wimbledon. "It's a bit disappointing for me because it's indoors, it's a court I like to play on," he said. "But I had my chances and missed them. When he had them, he was very committed. I think that was the difference today."Only six men have ever beaten #Federer & #Nadal in the same tournament.
— Live Tennis (@livetennis) November 18, 2017
.@David__Goffin is now among them.
Hell of an #ATPFinals debut. pic.twitter.com/5so8HMLObd
It was the first time in the tournament's history that three debutants reached the semi-finals. With Djokovic and Andy Murray missing from the eight-man field and Nadal forced to pull out injured after his loss to Goffin, Federer was strongly fancied to romp home. But his departure means there will be a new name on the trophy on Sunday. That could be Dimitrov, who roared into a 3-0 lead in the first set before Paris Masterschampion Sock won six games out of seven to take the first set. Undaunted, Dimitrov, 26, stepped up his game and bagelled the 25-year-old eighth seed in the second set in just 22 minutes to take the match into a decider.1st victory over Roger Federer
— ATP World Tour (@ATPWorldTour) November 18, 2017
1st final at the #NittoATPFinals
"I have no words. I cannot describe how I'm feeling... so much joy, so much happiness." - David Goffin
➡️ https://t.co/UxMNQRYo07 pic.twitter.com/xs3YHpTsxB
In an enthralling third set, neither player was able to force a break until the crucial eighth game, when Dimitrov hit a forehand winner down the line to lead 5-3 after a double-fault from Sock. He held his nerve to seal the contest on his fourth match point in a game lasting around 10 minutes. "I was very composed with myself, I didn't let any negative thoughts come into my head," said Dimitrov. "Things went my way tonight and I'm more than happy. "I'm so humbled to be in the final tomorrow. It's another match -- I just need to keep on playing. It's the last match of the season so full house, and we're on."He's done it!
— BBC Sport (@BBCSport) November 18, 2017
David Goffin beats Roger Federer to make it through to the final of the #ATPFinals.
He wins 2-6, 6-3, 6-4.
What a performance. ??https://t.co/GdtjZTsiVG pic.twitter.com/n0TMCk6489
What a week! ?
— ATP World Tour (@ATPWorldTour) November 18, 2017
David Goffin beats Roger Federer 2-6 6-3 6-4 to reach the championship match of the #NittoATPFinals ➡️ https://t.co/UxMNQRYo07 pic.twitter.com/QfyqS7dXat