Shanghai - World number one Novak Djokovic survived an almighty scare against 110th-ranked Mischa Zverev as he fought back from a set down to reach the Shanghai Masters semi-finals on Friday.
The defending champion, who has been struggling with motivation and injuries, lost the first set and was then taken to a second-set tie-break as tensions rose at the Qi Zhong Tennis Centre.
But qualifier Zverev's composure cracked as the 12-time Grand Slam-winner reeled off the first four points of the tie-break and raced through the deciding set to win 3-6, 7-6 (7/4), 6-3.
Djokovic avoided what would have been the most humiliating defeat of his season and maintained his record of reaching the semi-finals in all seven visits to the tournament.
It has been a troubled few months for the Serb, who said he had lost motivation and complained of "private issues" as he suffered shock early defeats at Wimbledon and the Olympics.
Chinese fans brandished Serbian flags but there was consternation when three-time champion Djokovic gave up an early break and sent down four double faults as he lost the first set.
Djokovic's misfiring serve cost him another two breaks in the second set but he also broke Zverev twice as they went to a tie-break and the German stood on the verge of a famous win.
However, a succession of Zverev errors effectively handed over the set before Djokovic took control against the tiring German and saw out the victory in two hours and 20 minutes.
In the semi-finals on Saturday, Djokovic will play Spain's Roberto Bautista, who floored Jo-Wilfried Tsonga 6-3, 6-4 to send last year's runner-up crashing out.
Bautista broke Tsonga three times in the first set and once in the second as he raced through in 72 minutes for his third win in a row over the Frenchman.