Alexander Zverev
Alexander Zverev reached his maiden Grand Slam quarter-final on Sunday, June 3.ERIC FEFERBERG/AFP/Getty Images

World number three Alexander Zverev expressed confidence that youngsters on the tour can break the dominance of Rafael Nadal and Roger Federer, the two veterans of the sport who are still atop the ATP rankings.

Concerns have been raised over the inability of tennis' new generation stars to challenge the seasoned campaigners. Since 2005, 50 of the 52 Grand Slam titles have been shared between five players — Federer, Nadal, Novak Djokovic, Andy Murray and Stan Wawrinka.

Tennis greats of the likes of Marat Safin had questioned the lack of upcoming superstars in tennis and lamented the worrying trend.

Federer, 36, and Nadal, 31, were hardly challenged by the chasing pack last year as the two legends shared all four Grand Slam titles between them after coming back from injury layoffs.

The Swiss great has started the ongoing season by defending his Australian Open crown while the King of Clay is favourite for an 11th French Open title.

Nonetheless, Zverev, who has been touted as the next-big-thing in tennis, is considered one of the main threats to Nadal in the ongoing tournament.

"I am top three in the world now. Other young guys are coming up strong - in the end we'll be very high soon," Zverev said, as quoted by the BBC.

"With time we will see who can become the next Grand Slam champion, who can become the next world number one. Right now Roger and Rafa are dominating, but we are doing everything we can to change that."

Zverev joins elite club with three straight five-setter wins

Zverev achieved a minor but what seems to be one of the most important breakthroughs of his nascent career on Sunday, June 3 as he reached his first Grand Slam quarter-final after 11 unsuccessful attempts.

The 21-year-old also achieved the landmark in style as he joined an elite club of eight players, the only ones to win three straight five-setters at Roland Garros. Notably, the German star needed three and 29 minutes to beat Karen Khachanov 4-6 7-6 (7-4) 2-6 6-3 6-3 in Sunday's fourth-round match.

Zverev has won eight titles, including three Masters 1000 crowns, at the tour level but his abilities to deliver at crunch moments and remain unaffected by fatigue were questioned following his dismal performances in Grand Slams in the past.

He will face clay-court specialist Dominic Thiem in what promises to be a mouth-watering quarter-final encounter. Despite having spent more time than anybody else on courts at French Open 2018, Zverev is confident he has the firepower to go the distance in Paris.

"I'm very happy about being in the quarter-finals here, going the hard way, going long distance every single time and showing myself, showing everybody, that I can play for as long as I need to," Zverev said.

The German youngster added: "If you're mentally fatigued, then something is wrong with you. Physically, obviously it's not easy to play, you know, back to back to back five-set matches, but I will manage it somehow. I will do everything I can to recover, as I said after the last match. I will make sure to be ready in two days' time."