Djokovic won three of the four grand slam crowns in 2021, Medvedev captured his first at the US Open while Zverev snared the Olympic gold medal and a second season-ending championship in three years.

The trio rightfully occupy the top three spots in the rankings but Zverev's claim last month that he and Medvedev have effectively replaced Roger Federer and Rafael Nadal in the Big Three nevertheless caused a stir.

"I think next year could be very similar to the last six months from this year," Zverev told Eurosport Germany's Das Gelbe vom Ball podcast.

"Before, there used to be always talk about Nadal, Federer and Djokovic - now the big titles were the Olympics, US Open, Turin and Wimbledon, and they were all won by Medvedev, Djokovic and me.

"I don't expect it to be any different next year."

The fourth-ranked Tsitsipas isn't so sure.

"Let tennis do the talking," the Greek told AAP following his season-opening loss to Diego Schwartzman at the ATP Cup in Sydney on Monday night.

"Look, we have a long year ahead of us. Let us all play our best tennis, and let's see who is the one that deserves it at the end of the year."

Like Zverev, Tsitsipas has yet to win a slam and, like the German, the 23-year-old lost his only grand slam final from two sets to love up.

With three other grand slam semi-finals to his credit, just like Zverev, Tsitsipas very much belongs a place in the Big Four.

His more immediate concern, though, is being fully fit for this month's Australian Open.

A wounded Tsitsipas offered conflicting messages over his Open participation after his painful loss to Scwartzman.

He battled valiantly for almost three hours before succumbing to the dogged and diminutive world No.13, having withdrawn from Saturday's scheduled singles match after undergoing elbow surgery in November.

"I don't know what my future plans are for this tournament. I'm not really sure," Tsitsipas said when asked about his Open hopes.

"I'd love to play, but I really don't know how I'm going to feel tomorrow.

"That was one of the biggest concerns - if I'm going to play this match today - how is the recovery going to be tomorrow?"

However, Tsitsipas subsequently told the official tournament website: "It was good to see myself perform at such a level. I didn't expect it.

"It worked out better than I thought. I was able to hit balls that I was scared to hit two weeks ago, so I'm heading towards the right direction.

"It gets better and better every single day almost. We have plenty of time before the Australian Open begins."

Australian Associated Press