Former world number one Novak Djokovic, the last surviving member of tennis' "Big Four", said he does not plan on stopping any time soon but admitted that the retirement of rivals Roger Federer, Andy Murray and Rafa Nadal has been overwhelming.
Djokovic, Federer, Nadal and Murray were dubbed the "Big Four" during a period of dominance when they won a combined 69 Grand Slam titles and were involved in some of the most memorable matches of the last two decades.
Spain's Nadal, who won a record 14 French Open titles, announced on Thursday that he would call time on his career after next month's Davis Cup. Murray retired after this year's Paris Olympics and Federer bowed out in 2022.
Speaking after beating Czech Jakub Mensik in the Shanghai Masters quarter-finals on Friday, Djokovic said: "(Nadal) has been my greatest rival. The rivalry I had with him has impacted me the most in my career by far.
"We knew that that moment is coming sooner than later, but it's still a shock, you know.
"Roger a few years ago, when he announced retirement and Andy as well this year. I mean, it's a bit overwhelming for me to be honest. I don't know what to make out of it. I still enjoy competing. But part of me left with them, a big part of me."
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In his 6-7 (4) 6-1 6-4 win over Mensik, who was born over a year after Djokovic played his first match on the ATP Tour in 2004, the Serb was pushed hard but fought back to clinch the win.
It ensured his progression to a record-extending 78th ATP Masters 1000 semi-final - two more than Nadal.
"These kind of matches, against teenagers, it's something that really motivates me," Djokovic told reporters after the win.
"It keeps me going, and pushes me to really dig deep, and to show to the world that I still got it in my legs, that I can still go the distance with the young guys.
"I'm super glad that I managed to win this very challenging match."
Djokovic faces world number seven Taylor Fritz in the semi-finals on Saturday after the American defeated Belgian David Goffin 6-3 6-4 earlier on Friday.
"I'm going to have a big server opponent tomorrow, Fritz, so I have to be ready for another difficult match," the 24-times Grand Slam champion said.
"Quick conditions, if you serve well it's quite a big advantage.
"We are entering the last couple of matches of the tournament, and now is the time for me to really try to step it up even more, and hopefully I can get a chance to be in the finals."
