Talented crop of young aces rapidly narrowing the gap on vaunted Big 3

China is bearing witness to a discernible power shift at the top of men's tennis as a surging youth brigade is gaining ground more quickly than expected.

Roger Federer, Rafael Nadal and Novak Djokovic have maintained a veritable stranglehold on the majors for the past decade, but the ATP is now straddling a chasm, with one foot firmly planted on the Big 3 and the other nudging the new crop into uncharted territory, wondering what the landscape will look like once the three titans retire.

The recent strong run by the post-1990 generation, highlighted by clean sweeps of all semifinal berths at two straight tournaments in China, indicates the change is happening even with the mighty trio still in their prime.

Last week's Rolex Shanghai Masters, the only ATP 1000 Masters event held in Asia, featured four semifinalists-Germany's Alexander Zverev, Stefanos Tsitsipas of Greece, Russian Danill Medvedev and Italy's Matteo Berrettini-all born after 1995 for the first time in the event's 11-year history and only the second time in the history of the 1000 series.

In Medvedev, the tournament also got its first champion in 10 years not named Federer, Djokovic or (Britain's former world No 1 Andy) Murray.

The Russian beat fifth seed Zverev 6-4, 6-1 in his sixth straight tour-level final on Sunday at Qizhong Tennis Center in western Shanghai.

The China Open, an ATP 500 event, also saw four post-90 players-Tsitsipas, Zverev, Austria's world No 5 Dominic Thiem and Russian No 9 Karen Khachanov-meet in the semis in Beijing a week before.

Although still far ahead when it comes to accumulated success at the Grand Slam level, the Big 3 said in Shanghai the gap between them and the next wave has become almost negligible.

"They're knocking on the door big time, the young guys," Federer said after his three-set loss to Zverev in the quarterfinals.

"It's an exciting time in tennis. Nothing new there... they're great. It's really open now."

With his hard-fought win over the 38-year-old Swiss legend, Zverev, 22, became just the third player on the tour to face Federer at least seven times and emerge with a winning record (4-3) against the 20-time major winner, joining world No 1 Djokovic (26-22) and No 2 Nadal (24-16).

The Big 3 have combined to clam 53 of the past 62 Grand Slam singles titles, stretching back to Wimbledon in 2004-more often than not facing each other in the finals.

Their momentum in this season's finishing stretch serves notice that next year will be extremely intriguing at the major level, Zverev reckoned.

"To be honest, I think a new Grand Slam champion will soon appear," said the German, who won last year's ATP Finals. "Next year, maybe the following year, but in the next two years I think 100 percent it will happen."

Tsitsipas, who overcame a first-set scare to stun Djokovic in a three-set quarterfinal victory to lead 2-1 in his career against the Serbian 16-time Grand Slam champion, could be that guy.

Chasing success against the Big 3 is helping him shake off the fear factor, once an obstacle for him to bring out his best, said the 21-year-old Greek.

"I always dreamed of beating those players, and I see each match as an opportunity to bring out my best ... it's a very big boost," added Tsitsipas, who upset Nadal in the semis at the Masters 1000 Madrid after defeating Federer in the quarterfinals at the Australian Open.

"I honestly feel like they are more threatened than I am, and I think also that kind of makes me more relaxed out on the court.

"Once you get aggressive and they see that you're really going for it, I might even say they get a bit scared."

German legend Boris Becker, a three-time Grand Slam winner and former world No 1, is encouraging the next generation to dare to think big in order to get over the mental hurdle of facing the maestros.

"It's not the forehands, it's not the fitness-it's a certain mentality, an attitude that makes the difference between winning and losing," said the 51-year-old winner of 49 ATP titles.

Coming up together, the current crop of youngsters also find motivation in each other's success.

"I think in the final of the US Open, Daniil played a great match," Italy's Berrettini said of Medvedev's five-set loss to Nadal in his major final debut in New York last month.

"That's motivation. I was playing with Daniil, Karen and Borna (Coric) in the juniors. They started to win titles and I said to myself, 'I can do that'. We are helping each other to get those achievements and it's really nice to have this kind of competition," said Berrettini, who lost to Zverev in straight sets in the Shanghai semis.