The Big Four in tennis has lasted longer than anyone could have predicted. Stan Wawrinka sometimes enters the conversation. But while undisputed No. 1 Novak Djokovic, ageless No. 3 Roger Federer, resurgent No. 4 Rafa Nadal, and resilient No. 2 Andy Murray have all switched places -- they've generally persisted as a quad at the top.
But how? Tennis is famously a young person's game -- historically most of the greats are past their primes by 30. Yet it's been a long while since the men's game has seen the great teen or early 20s player serve notice to the world, the way Boris Becker once did at Wimbledon and Nadal did as a 19-year-old French Open champ. With Wimbledon imminent, where are the young challengers? Federer was just beaten at Halle by the 19-year-old German rising star Alexander Zverev. But that's the first time a teen has beaten a top 5 players since Murray lost to Borna Coric, 18, last year in Dubai. Domimic Thiem, at age 22, is the youngest man in the top 10 world rankings (No. 8). Ranked No. 7, Milos Raonic is next youngest in age -- he's 25.The BEST SALES on Amazon NOW ]