Younger players had breakthrough season in 2021 - Zverev

German world No 3 Alexander Zverev believes 2021 has been a breakthrough season for the younger generation despite world No 1 Novak Djokovic winning three out of the four Grand Slam titles during the year.

The so-called 'Big Three' of Djokovic, Roger Federer and Rafael Nadal have dominated men's tennis for more than a decade but in 2021 the younger players have enjoyed more success.

Though Federer and Nadal missed the chunk of the year due to injuries and world No 1 Djokovic skipped a number of tournaments to concentrate on winning more major titles, Zverev feels the younger players now have more momentum.

World No 2 Daniil Medvedev beat Djokovic to win the US Open final and deny the Serbian a calendar Grand Slam in September.

"First of all, we're not young anymore," the 24-year-old Zverev told reporters on Friday ahead of the season-ending ATP Finals in Turin, Italy.

"We did make a big step forward this year. The young guys have won all the Masters (1000 titles) apart from Rome and Paris. My winning the Olympics was a big statement. Daniil winning the US Open was a big statement."

Nadal, ranked sixth, is a year older than the 34-year-old Djokovic and the next oldest players in the current men's top 10 are 25-year-olds Medvedev and Italian Matteo Berrettini.

"I think the young guys are coming through and it's a natural curve," Zverev said, adding that Djokovic is "deservedly" the No 1 for winning three majors in 2021.

"The top 10 is definitely getting younger. I think that's a good thing for our sport as well."

World No 3 Zverev, who won the 2018 ATP Finals title, has been drawn in the 'Red Group' alongside defending champion Medvedev, local hope Berrettini and Poland's Hubert Hurkacz.

"I think I've played good tennis this year. There is a reason why I won five tournaments, there is a reason why I'm the only person that won multiple Masters this year. Also at the Olympics, I have a gold medal," he said.

"I do look forward to this week, to the tournament. I want to do well, and I want to win matches here, that's for sure."