Novak Djokovic could still win three majors next year but Gilles Simon reminded tennis fans the world number one is not "eternal" as he heads towards the end of his career.

Djokovic triumphed in three of the four majors in 2023, with September's US Open success taking him level with Margaret Court's record 24 grand slam triumphs.

Defeating Daniil Medvedev in the final, Djokovic – aged 36 years and 111 days – became the oldest winner of the men's singles title at the US Open, as well as winning a trio of majors in a year for the fourth time.

That saw him surpass Roger Federer – who won three grand slams in a year on three occasions.

Simon, though, warned that Djokovic cannot play on forever.

He told Stats Perform: "I think he can win some [majors, but] I think he's getting to an age where it is going to become difficult.

"Most of the observers want to believe that a player is eternal but none are more eternal than the others.

"I think he can win a lot next year; will he win one, two or three? Next year he can do one more big year, but I also think that it will be his last."

The 36-year-old Djokovic acknowledged the retirement speculation after his US Open victory, asking how long he can continue.

Simon likened the twilight of Djokovic's career to fellow great Federer, whose playing days were curtailed by injury and fitness issues.

"At one point like every player there's going to be a break, that was the case for Roger Federer, remember when he won in Australia at the age of 37 playing incredible tennis," Simon added.

"At Wimbledon, he could have won because he lost against Novak Djokovic on match point. Time never had a grip on him, he had never been injured, he played really well, and then all of a sudden he disappears."

Another of tennis' 'Big Three', Rafael Nadal has not played since January 18 at the Australian Open – again owing to injury problems as years of toiling on the court takes its toll on even the best.

"We have Rafael Nadal who we hope to see again next year, who got us accustomed to more traditional injuries, longer injuries and with doubts," Simon continued.

"Once again he wins the Australian Open, he wins at Roland Garros even with his history with his foot, he again has a semi-final at Wimbledon.

"We say no about Novak because he is more careful, but we said the same about Federer, he expends less energy, he has a more fluid game and technique, he preserved himself from injury.

"I think next year will be very interesting because it’s a year where he can again win, where he still has an advantage [ahead of the rest] but we saw him lose against [Carlos] Alcaraz at Wimbledon.

"I thought he would have more advantage on grass because of the experience he has compared to others and his game works so well on grass – but he is beatable."

Age has shown no sign of slowing Djokovic down yet after he lifted the Paris Masters trophy for a seventh time on Sunday, defeating Grigor Dimitrov in straight sets.

That victory marked his second hard-court ATP-1000 title of 2023, Djokovic managing multiple Masters titles in a single season for the ninth time in his career. Only Federer, having won multiple such events in a year six times in his time, can get near to that feat.

Yet Simon suggested 30 major triumphs may be out of Djokovic's reach due to the emergence of Alcaraz, who won at Wimbledon this year, and a gruelling schedule.

"He's so strong he knows how to prepare himself, but he can't do a series of tournaments," said the Frenchman, who won 14 career titles and reached a high of number six in the ATP rankings.

"If everything was going well he would be playing every week like when he was 25 years old, so that is what is missing.

"He looks after himself, ultra-professional and very strong. The US Open was important for him, I see him maybe doing one or two next year, but I am waiting to see for the next few years after that.

"I can't see him reaching 30 [majors] for example when Carlos Alcaraz could win two or three a year – I wish it for him but I don't see it like that."

The Rolex Paris Masters became the first Masters 1000 to broadcast its qualifying matches on Twitch, live on Rivenzi's channel.