Alexander Zverev ended Roger Federer’s campaign for a 100th career title after he conquered the Swiss 7-5, 7-6 (7-5) to reach the ATP Finals championship match in London on Saturday.
Zverev secured the first set with a single break at 6-5 after two Federer errors handed the lead to the world number five.
Federer broke first in the second set for 2-1 but couldn’t consolidate an advantage as Zverev battled back to force a tie-break and claim victory with a backhand volley after one hour and 35 minutes.
The 21-year-old is the first German to make a season-ending final since Boris Becker in 1996.
Zverev will play world number one Novak Djokovic after the Wimbledon and US Open champion dismissed Kevin Anderson in a dominant 6-2, 6-2 win in the other semi-final.
Djokovic broke Anderson’s serve twice in a one-sided first set as the South African could not cope with Djokovic’s supreme rallying.
Anderson, the first African player to ever feature at a Finals tournament, had his serve broken twice more in the second set before Djokovic wrapped up the win in 75 minutes to enter his seventh year-end championship final.
The faultless Djokovic has not been broken on serve all week in the English capital, facing only two break points, and only dropping seven total service points against Anderson.
“I thought I was also backing up the serve with the first shot in the rally very well through the entire week,” said Djokovic.
“That allowed me to kind of protect my service games, win them all so far in the tournament.”
He will aim to equal Federer’s leading haul of six ATP Finals crowns when he meets Zverev in a Sunday’s final.
Djokovic has only lost one of his last six ATP Finals and that came against Britain’s Andy Murray in 2016.
In a close first set, Federer only dropped nine points on serve but two of those points cost him the lead.
The 37-year-old , who was aiming to make his 11th championship final, netted to open up set point before he fired a forehand wide to fall behind.
However, Zverev’s triumph was not without controversy due to a ball boy’s mistake when he dropped a ball at a vital moment in the second set tie-breaker.
Federer was leading the tie-break 4-3 when, in the middle of a rally, a loose ball rolled and the point had to be replayed.
“Without even thinking, I stopped the rally, said it was a let. That’s how it is with the rules,” said Zverev, who still apologized to a pro-Federer crowd among a chorus of boos at the O2 Arena.
“Obviously the crowd didn’t appreciate it, which I was a little bit upset – not upset, but I was a little bit sad at the end with the booing and reaction of the crowd.
“Maybe they didn’t know what actually happened. That was maybe part of the reaction.
“I said sorry to Roger at the net.”
An ace allowed Zverev to level proceedings before a weak shot into the net from the 20-time grand slam winner Federer opened up two match points.
“I got aced. So, yes, it did affect me,” said Federer of the controversial point.
“It was obviously a big call. It could have made a difference. That’s all hypothetically speaking now at this point.”
Zverev flicked a forehand long to waste one match-winning chance but on the next point, he arrived at the net to collect the best win of his young career.
Before Sunday’s final, Djokovic has an edge in confidence after he beat Zverev in the group stages earlier this week with a 6-4, 6-1 victory.
“I’m expecting quite a different match-up for us tomorrow than what it was in the group stage,” said Djokovic.
“Even though the win in the group stage against him few days ago can definitely serve as kind of maybe a mental advantage. He’s shown why he deserves to be in the mix of the top players in the world.”
Meanwhile, Zverev wants to ensure he doesn’t make the same mistakes in the final when he will get the chance for a rematch.
“Novak right now is the best player in the world. It’s very tough to beat him,” said Zverev.
“I’ll try to hit more winners and less unforced errors. I’ll be ready.”