Stefanos Tsitsipas has reached the final of the ATP Finals in London after seeing off a profligate Roger Federer 6-3 6-4.
Federer had a chance to break the Tsitsipas serve in the opening game of the match but squandered that opportunity and soon found himself 3-0 down with a couple of lax smashes.
Though the Greek went on to win the first set, it was far from routine, with Federer missing a further three break points at 4-2, and two more as Tsitsipas squandered six set points before finally clinching it 6-3.
Tsitsipas was the first to break in the second set as well, with Federer sending a tame forehand into the net.
He immediately leapt into a 0-40 lead but saw another three break points drift away but a superb forehand winner and a wonderful drop shot brought up his 10th break point of the contest, which he finally converted.
Tsitsipas edged ahead again as Federer threw in a slack service game and this time was able to build on his advantage and move 4-2 in front.
The 38-year-old was some way off his extraordinary level of performance against Novak Djokovic on Thursday but still crafted two break back points as Tsitsipas tried to serve it out but failed to take them and his young opponent held his nerve to reach the biggest final of his career.
"Wow! Jesus. I'm so proud of myself today," he said on court after the win.
"Great performance and once again, people were great. I really enjoyed my time on the court and sometimes matches like this, you wonder yourself how you overcome all those difficulties, all those break points down. It's really, like, a mental struggle.
"So I'm really proud that I managed to save so many break points today. You know, I was trying not to give an easy time to Roger. He was playing good and shout out to him as well. He did pretty well this week in Nitto. I mean, an inspration, obviously, as always.
"Playing him, it's the biggest honour I could have. Today's win, victory is probably one of my best matches of this season. And these are the moments that I always wait for and these are the moments that I want to prove the best out of my game."