Khachanov hammers ailing Zverev in Paris Masters

Khachanov, at 22 another of the sport's brightest prospects, took ruthless advantage of the 21-year-old German's physical struggles as Zverev, battling with shoulder trouble, needed a medical time out in the first set at 4-1 down.

Nonetheless, the Muscovite deserved all the credit for the quality of his power game as he broke the world number five's serve six times in 70 minutes to set up a last-four meeting with either Jack Sock or Dominic Thiem, who were playing later.

Zverev looked frustrated at his serving woes and being pushed around by the world number 18. At the end of a one-sided first set, he complained to Khachanov about the over-zealous reactions of the Russian's camp at courtside.

"When you are losing, maybe you get frustrated from some calls from somebody in the crowd and maybe he was pissed, I don't know, that somebody from my box screamed on his mistake and that was the reason," Khachanov told Sky Sports afterwards.

"But then we're good friends outside the court and everything is fine."

Zverev, who has qualified for the ATP Tour Finals for the second year running, offered his point of view.

"I told him my shoulder is hurting and that his uncle, or something, that he's going a bit crazy," he said. "And I told him to tell him to keep it down a little bit because he was going a little bit too much over the edge.

"I was never going to win the match, so it was just I told him to calm down a little bit."

Zverev had defeated Khachanov in their previous two meetings, including a fluctuating five-setter also in Paris in June at the French Open, but the Russian dominated from the outset this time.

"It was really tough for me to lose that match in Paris," said Khachanov, who had been leading two sets to one at Roland Garros.

"So I was fully prepared, I've been playing some good tennis in the last couple of months and believing in myself so I didn't expect to be that easy in the score. But I played really well."

With two indoor hard court tournament triumphs to his name already this year, Khachanov will now move up to at least a career-high number 13 in the world next week.

In the evening session in Bercy, Novak Djokovic, fresh from regaining his world number one ranking, plays Marin Cilic and could set up the other semi-final with Roger Federer, who faces Japan's Kei Nishikori.