Novak Djokovic's latest victory over Roger Federer was among the toughest and best in their epic rivalry, a 7-6 (6), 5-7, 7-6 (3) feast of attacking tennis which had the roaring crowd on their feet and remained in doubt until the very end.
It finally ended, after three hours, when Djokovic moved 6-1 up in the tiebreaker. Federer saved two match points but cracked in a long rally and chopped a backhand into the net.
"We had epic matches throughout our rivalry but this one definitely ranks as one of the best," Djokovic said.
Djokovic's fourth straight win over Federer and 25th in 47 contests sends him into the final against unseeded Russian Karen Khachanov, who has never played in a Masters final.
"This is my best match of the year, that's for sure," Djokovic said, addressing the crowd in French. "Big respect to Roger."
Federer remains one short of 100 career titles.
"When you lose a close match like this you always have regrets," a disappointed Federer said. "That's why I guess I have this face right now."
Djokovic is on a 22-match winning streak and will aim to move level with Rafael Nadal on a record 33 Masters titles.
"Novak is obviously on a roll," Federer said. "You can feel it."
Khachanov, who beat Dominic Thiem 6-4, 6-1, won the Kremlin Cup in Moscow last month for his third career title.
Djokovic, who beat him on the way to the Wimbledon title, is seeking a record-extending fifth Paris Masters title and 73rd title overall.
He was made to work far harder than when he beat Federer in the Cincinnati Masters final in August.
After they hugged at the net, Federer walked off quickly and raised a thumb to the cheering crowd.
"People enjoy the rivalry. We do as well," Federer said. "It's tough and fair, the way it's supposed to be."
Fans got everything they could have hoped for: Two players with a combined 34 Grand Slam titles, 59 Masters titles, and 533 weeks at No. 1 slugging it out at a level of unrelenting yet sublime intensity.
Brilliant one-handed winners on the run from Federer down the line and acute-angle volleys at the net; astonishing elasticity while retrieving from the baseline and laser-beam forehands to the corners from Djokovic.
Federer had 17 aces, while Djokovic got five of his eight in his last three service games of the match, raising his level at the right time.
Djokovic briefly let his volatile temper get the better of him, though, when he had Federer at 15-40 down in the ninth game of the deciding set. Federer saved both break points, and Djokovic whacked his racket into the ground, drawing the first and only boos of a titanic match.
Djokovic held his hands up as if to apologize to the unforgiving crowd, unhappy that a pique of rage interrupted their gourmet feast of tennis.
Brimming with confidence in a season which has seen him go from No. 22 in the rankings in May to No. 1 when they are released on Monday, and in which he also added the U.S. Open to his Grand Slam haul, Djokovic created pressure throughout.
But Federer saved every break point — 12 of them — and secured the only break of the match in clinching the second set.
"Hasn't happened too many times that I don't break a serve of anyone, especially if I have 12 break points," Djokovic said. "Most of the break points he just served well, and played great shots."
The best one of the match went to Federer in the eighth game. As Federer charged to the net, Djokovic hit a powerful forehand which clipped the net and flew to the left of Federer, wrong-footing him. From a seemingly impossible angle, and totally off balance, he scooped his racket behind his neck and flicked a volley over the net for a winner.
Federer thrust his arms into the air, the crowd rose to their feet in sheer disbelief.
Even by Federer's lofty standards, it was remarkable.
"That's why he is who he is," Djokovic said, admiringly.
But after losing the match, Federer was left shaking his head. He was unhappy with someone in the crowd twice shouting "out" during the long match-point rally.
"It's just unfortunate it happens and at the end you lose the point, the match," Federer said.
Still, he retained a sense of irony.
"Thank God the rally ended," he said. "It would have been five times if it continued."