Tennis' popularity might take a hit once Roger Federer and Rafa Nadal announce their retirements given the lack of consistent challengers, according to former world number one Boris Becker.
Neither player is showing signs of considering retirement but Becker, a six-time Grand Slam champion, feared that the sport could not carry on with just Novak Djokovic and Andy Murray who, together with Nadal and Federer, are termed the 'Big Four'.
These four have dominated men's tennis for the past decade, sharing 41 of the last 48 Grand Slams.
What if Roger decides to quit or Rafa is not coming back?
"I think the men's side is in a very healthy state," said the 47-year-old Becker who is currently coaching world number one Djokovic.
"We have an increase in popularity from over 10 years ago and the numbers are staggering.
"But the question has to be asked: what if Roger decides to quit or Rafa is not coming back? It's impossible to carry on with only Novak and Andy."
Federer is currently ranked number two and will target a record eighth Wimbledon crown when the 2015 tournament starts on June 29.
Nadal, meanwhile, is a 14-time Grand Slam winner but has fallen to 10th in the rankings, his worst in a decade.
He has also been seeded 10th for Wimbledon which is his lowest at the tournament.
Becker mentioned that Australian youngsters like Nick Kyrgios, who famously upset Nadal at Wimbledon last year, and Thanasi Kokkinakis had good personalities and were exciting to watch.
"But there's a gap in between and there are players you don't know anything about. In two or three years' time, we have to be careful."
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Source: Al Jazeera