Novak Djokovic held his nerve during a tense tie-break to beat Nuno Borges 6-3, 7-6 (7/2) at the China Open on Wednesday and extend his extraordinary unbeaten streak in Beijing.

The 39-year-old Serbian was struggling physically but pushed through the second-set decider for his first win at any event since Wimbledon in July.

The former world number one is set to meet wildcard Bu Yunchaokete of China in the second round.

Fans packed the stands in Beijing to watch Djokovic, a firm favourite in China who has never lost in Beijing in 30 matches — although this was his first match at the event since 2015.

He delighted the crowd with an ace to end the first game and saved two break points after a pair of double-faults to win the first set.

Djokovic has had health issues in recent months and struggled to pick up points at the start of the second set, using his racquet to stretch his back between games and needing a medical timeout as a trainer worked on his right shoulder.

But he forced a path to victory in one hour and 50 minutes, clinching it when Borges, the world number 49 from Portugal, returned into the net.

It preserved Djokovic’s winning streak in Beijing, where he has won six titles.

Earlier, Karen Khachanov swept aside second seed Felix Auger-Aliassime 6-3, 6-3 in their first-round meeting.

Khachanov, the world number 26, won three straight games, taking the first set in 31 minutes.

The 30-year-old then kept his cool to break Auger-Aliassime on the first match point, wrapping things up in one hour and 11 minutes.

He faces either Arthur Rinderknech of France or qualifier Alex Molcan of Slovakia in the round of 16.

Khachanov brushed off suggestions he had Auger-Aliassime’s card marked following his second statement win over the Canadian world number five in a matter of weeks.

“It was a tough match,” the Russian, who triumphed at the US Open, said.

“When you approach this match, you are thinking it’s a completely new match, completely different. In China, in Beijing. Different court, different balls.

“You just focus again from zero. You know that what you did well… and you just try to keep the momentum going. There is not much secret about it.”