(REUTERS, AFP) - Men's world No. 1 Novak Djokovic continued his dominant form in Tokyo to storm past Frenchman Lucas Pouille 6-1, 6-2 and into the semi-finals of the Japan Open Tennis Championships on Friday (Oct 4).

The Serb has served with ruthless efficiency in his previous two matches and more of the same was on display, as the 32-year-old fired eight aces and won 82 per cent of points on his first serve to swat aside fifth seed Pouille in 50 minutes.

Up next for the 16-time Grand Slam champion, who has yet to drop a set in his first Japan Open, is 2017 winner David Goffin or Chung Hyeon, who are in action later.

Meanwhile, Rafael Nadal has pulled out of next week's Shanghai Masters owing to a wrist injury that cut short his participation in last month's Laver Cup, the world No. 2 said.

The 33-year-old, who claimed his 19th Grand Slam title at this year's US Open, said that he had not had enough time to practise sufficiently due to inflammation in his left wrist.

"I am very sad to announce that I won't be able to play in Shanghai this year. It is the second year in a row and in China I have great fans," he said in a statement.

"But, as you all probably know, I had an inflammation on my left wrist during the Laver Cup and I haven't had the time to recover and practise to be ready... I hope to be back in Shanghai for the 2020 tournament."

The two-time finalist's withdrawal denies fans the chance to witness the reunion of the Big Four of men's tennis at the Oct 6-13 tournament, with Roger Federer, Djokovic and Andy Murray all scheduled to feature. It also hands Djokovic the advantage in the battle to seal the year-end No. 1 ranking.

In Beijing, Andy Murray said that his comeback from career-saving hip surgery was progressing better than expected despite going down fighting in the China Open quarter-finals.

The 32-year-old Briton lost 6-2, 7-6 (7-3) to top seed Dominic Thiem, but said: "I think this (week) was maybe the best in terms of how I played since I came back.

"It was great for me, I played three matches in four days, which is quite a lot.

"Actually I felt better than I expected today, as well," said the former No. 1, who had a major operation in January and returned to singles tennis only in August. Asked by AFP if he was further ahead than he expected to be in his comeback, he replied: "Yeah, maybe.

"I'm getting there, this week is better than last week, I hope next week is better than this week," the three-time Grand Slam champion said.

"That's how I have to try to keep going to see where my limit is, I don't think I'm at that limit now. "I think I can keep improving. That's what this week has shown me."

Women's world No. 1 Ashleigh Barty battled into the semi-finals with a gutsy three-set victory over familiar foe Petra Kvitova.

The Australian came from a set down to win 4-6, 6-4, 6-3 and plays Ukraine's Elina Svitolina or Kiki Bertens of the Netherlands in the last four.

This was the sixth meeting between Barty and two-time Wimbledon champion Kvitova, with the Australian winning only one of her previous encounters against the Czech.

Barty, 23, who had strapping on her left calf, was under pressure immediately in the deciding set after seventh-ranked Kvitova broke her first service game.

But the reigning French Open champion grabbed the break back immediately and, with the clock ticking past two hours on court, broke Kvitova again for a decisive 5-3 lead.

The Japan Open is Djokovic's first tournament since retiring from his US Open fourth-round match against Stan Wawrinka because of a problem with his left shoulder.

He has now reached at least the semi-finals in six of his past seven tournaments going back to the Madrid Open in May.

Big-serving American Reilly Opelka ended local favourite Yasutaka Uchiyama's hopes of a maiden ATP Tour semi-final appearance with a 6-3, 6-3 victory over the qualifier.

Opelka, who won his first title at the New York Open in February, next takes on qualifier John Millman in what will be their first career meeting.

The Australian eased past Japan's Taro Daniel 6-4, 6-0.

In China, Murray had the Beijing crowd behind him against the Austrian Thiem, ranked fifth in the world to his opponent's 503rd.

But he lost his first service game, putting himself under pressure immediately.

At times there were shades of the player who topped the world rankings in 2016, but the second set started in the same way as the first, the Briton having his serve broken.

Murray, who says that he now has no pain in his hip and it is a question of building up match fitness, looked down and out as Thiem served for the match. But he does not know how to quit and a nervy Thiem surrendered his service game for 5-5.

Murray went up 6-5, before Thiem forced the tiebreak. He carried that momentum to victory and the 26-year-old Thiem plays Karen Khachanov of Russia in the last four.