Djokovic proves staying power as he progresses to Shanghai semifinals

SHANGHAI, China — Novak Djokovic proved his staying power on Friday, beating an opponent 18 years his junior 6-7 (4/7), 6-1, 6-4 to claim the last spot in the Shanghai Masters semifinals.

The 37-year-old's victory over the Czech Republic's Jakub Mensik came a day after one of his greatest rivals and contemporaries, Rafael Nadal, announced he would retire in November.

The Serb, who is aiming for a 100th singles title in Shanghai, will next face world number seven Taylor Fritz after the American beat Belgium's David Goffin 6-3, 6-4 earlier on Friday.

"Overall, big battle, it took the best out of me to win it," said Djokovic after the match.

Both Djokovic and 65th-ranked Mensik brought serious firepower to the court, their hard-hitting rallies driving the stadium wild with tension.

The first set was closely fought, with Djokovic's break in the ninth game matched immediately by Mensik in the next.

The veteran pulled ahead early in the tiebreak, but seemed to lose focus, allowing the 19-year-old to come from behind to win.

The 24-time Grand Slam champion dominated the second set though, breaking in the second and sixth game.

Mensik recovered to pile on the pressure again in the third, but Djokovic got a crucial break in the fifth game to be crowned winner.

Djokovic called his opponent "one of the best players we have on the tour", adding "the future is very bright for him".

"These kind of matches against teenagers is something that really motivates me... and pushes me to really dig deep and to show to the world that I still got it, you know, and my legs can still go the distance with the young guy," he said.

- 'End of an era' -

The fact Djokovic's triumph came the day after the retirement announcement from Nadal -- who he called "the greatest rival that I ever had" -- was not lost on him.

"I'm a bit overwhelmed, to be honest, but, you know, I still have the desire to play," the Serb said of being the last man standing from tennis' golden era.

The 26-year-old Fritz, who said he grew up watching Nadal on television, said it was "the end of an era".

The American quickly took charge in the first set of his earlier match, breaking the 66th-ranked Goffin in the second and sixth games.

Underdog Goffin -- who knocked out second seed Alexander Zverev in the last round –- looked stronger in the second set, but ultimately couldn't replicate his feat with another top 10 scalp.

It is the first time US Open finalist Fritz has progressed past the third round in Shanghai.

He has lost to Djokovic at every one of their previous nine encounters.

"We've played a lot of times and I've never gotten him... (So I'm) waiting for that time that, you know, maybe I can get a first win on him," said Fritz.

"I'm only getting better and better, and I'm excited for the opportunity to play him."

Djokovic said he expected the match-up to be tight.

"It's the final stages of a tournament, anybody can beat anybody. I'm going to need all of my speed, all of my precision, all of my strength," he said.

World number one Jannik Sinner booked his place in the semifinals on Thursday, as did Mensik's compatriot Tomas Machac, who upset four-time Grand Slam champion Carlos Alcaraz.