Novak Djokovic needed a third set tiebreak to squeeze past world number five Stefanos Tsitsipas 6-2, 3-6, 7-6 (7/4) on Saturday and reach the final of the Paris Masters.
The Serbian will face Danish teenager Holger Rune who earlier beat in-form Felix Auger-Aliassime 6-4, 6-2 to reach a first Masters final.
"It's very sweet, obviously, when you win matches like this against one of the best players in the world," said Djokovic, who is bidding for a record-extending seventh Paris crown and 39th Masters triumph.
An eighth successive win over the Greek, extended the Serbian's overall winning streak to 13 matches.
Djokovic had the chance to take charge of the third set when he had two break points at 4-4. He was unable to convert either and the match went to the tiebreak.
After falling behind in a mini-break, Djokovic took the final four points to win the match after two hours 20 minutes on court.
"I thought I started the match very well, again, great hitting like yesterday in the quarters," said Djokovic.
"I had chances early on in the second, I didn't break his serve. The momentum shifted, the crowd got into it. I think he elevated his level of tennis.
"Deservedly so, we went into — both of us — into an even battle all the way until the last point, until the last shot. Some incredible points towards the end. I'm just really glad to overcome this challenge."
In spite of the defeat, Tsitsipas can still finish the year as world number one if he wins the ATP Finals following Carlos Alcaraz's decision to skip the Turin tournament because of the abdominal tear that forced him to retire from his quarter-finals against Rune.
- 'Super happy' -
In his semi-final, Rune avenged his loss to Auger-Aliassime in last weekend's Basel final to book his place in a fourth successive final.
"I lost to Felix last week in two sets, beat him this week in two sets. I learned a lot from last week, and trying to do a lot differently today. I'm super happy that it worked," said the 19-year-old.
A quarter-finalist at this year's French Open, Rune collected his fourth straight victory over a top-10 player this week by ending Auger-Aliassime's 16-match winning run.
The Canadian was attempting to become the first man to win four tournaments in as many weeks since Ivan Lendl swept five over a five-week span in 1981.
Auger-Aliassime paid the price for a hesitant swinging volley after a gentle looping return from Rune as he conceded the lone break in the third game of the opening set.
Rune then broke the eighth seed twice in succession to start the second set, inflicting a first defeat on Auger-Aliassime since his first-round loss at the Astana Open a month ago.
"You're always a bit more nervous when it's the final because it's so close to winning the tournament.
"It's going to be super tough... For me it's just really about playing my game because that's what can get me the closest to winning tomorrow."
Having arrived in Paris with just three wins at the Masters level, Rune began his run to the final by saving three match points to beat three-time Grand Slam champion Stan Wawrinka in the first round.
He then took down Hubert Hurkacz followed by Andrey Rublev before seeing off Alcaraz as the world number one retired with injury while trailing by a set Friday.
"Often it's like this. You're on the edge to lose and then you go deep in the tournament. Hopefully I can go all the way," said Rune.
Rune will break into the top 10 for the first time if he wins the title.