Novak Djokovic struggled to subdue German Mischa Zverev, with the two-time champion scratching out a 3-6 7-6 (9-7) 6-3 escape on Friday to reach the semi-finals of the Shanghai Masters.

Top seed Djokovic had his troubles with the 29-year-old qualifier whom he last faced in 2009.

Zverev swept the opening set but was unable to maintain the pressure on Djokovic in a second-set tiebreaker before going down in the third after almost two-and-a-half hours.

“I wasn’t striking the ball very well from the beginning of the match, to be honest,” Djokovic said. “I was quite flat with my feet, so he got me where he wanted to get me, and to stand still at the baseline.

“He was fighting; he was focused. He gave his best, and he was a few points from winning.”

Despite 37 unforced errors including six double faults, Djokovic remained composed. He smiled after his miscues and, at one point, even hummed a song.

“It was towards the end of the match. Instead of the occasional tantrum that I used to have – I hope it’s behind me – I would switch that vibration and transform it in a tune.”

Djokovic is keeping his nose ahead of Andy Murray as the Scot works to seize the year-end top ranking from his rival. Murray won the Beijing title last week to keep his momentum revved up in the ATP points chase.

Murray, seeded second, was later facing Belgian 11th seed David Goffin. The Scot leads the ATP with 62 match wins.

Djokovic moved into a semi-final contest with Roberto Bautista Agut after the Spanish 15th seed upset No.9 Jo-Wilfried Tsonga 6-3 6-4.

The French threat has been dealing with autumn knee problems and is only just back on the circuit after quitting a US Open quarter-final with his injury.

“It was a little surprised to play like this (this well) this week,” Tsonga said. “I hope I will continue to improve like this in the next few days and play better in the next tournament.

“Today was still good. I just lost to a guy who was better than me.”

Bautista Agut has reached his second Masters 1000 semi-final after 2014 Madrid.

“I’m happy about being in the semi-finals. But also, I’m happy with the way I’m working, with the way I’m playing on the court,” the Spaniard said. “I’m feeling great. I hope to continue like this.”

Djokovic has reached his seventh Shanghai semi-final in as many attempts; he stands 21-1 at the venue, losing to Roger Federer two years ago in the semi-finals.

The Serb also added his 30th win at a Masters 1000 against two defeats.