"I mean, unless it's somebody 17, 18 who is, you know, 6-5 and really fully developed, it's gonna be tough,'' said Donald Young, who first competed in a Grand Slam event at 16 and counts himself a major champion wannabe at 22. "Mentally, also. I don't know what the stat is in the top 100, but someone told me the average age is 26 or something like that and the top 10 is 27.
"Your body is probably not ready to do it day in and day out against grown men who are working very hard."
In the women's game, the classic early burnout of Jennifer Capriati, who turned pro at 13 and was an Open semifinalist at 15, frightened women's tour officials into handing down a 1994 edict -- the "Capriati Rule" -- that barred players from turning pro before their 14th birthday and limited how often teenagers could play.
What was meant to protect young players against early-onset retirement also curbed their ability to develop at a quicker pace, though the Williams sisters -- who came to the tour in their late teens, packing heat and ready and able to take on the world -- quickly blew holes in that theory.
More to the point, probably, is how rapidly the sport now demands players jump through rigorous training hoops if they hope to be contenders. Kimiko Date-Krumm, now 40 and back from a 12-year tennis sabbatical in 2009, has found that: "When I go to the gym now, everybody is there. They're all more powerful, more physical.''
Novak Djokovic won his first major title, the Australian Open, at 20, but it wasn't until this year, at 24, that he reached No. 1 and became a legitimate threat to the two-headed Roger Federer-Rafael Nadal monster.
"It takes a while to really understand the game, understand the life,'' Djokovic said, "and you learn from your mistakes, obviously. It takes time for the body to develop, to get stronger and get experience.''
Tracy Austin and Martina Hingis won the Open at 16, Monica Seles at 19. Michael Chang was 17 when he won the French Open, Pete Sampras 19 when he won his first of 14 majors. But the last female teen to win a Grand Slam event was Maria Sharapova, at 19, in 2006; the last male, Nadal, at 19, in 2005.
"Physically,'' said Chris Evert, who was 19 when she got her first major trophy, "it's stepped up to a higher level in fitness. And there's maturity. The days of 15- and 16-year-olds winning Grand Slams, those days are over. You're asking for a well-rounded athlete, physically and mentally. Listen, I didn't have a great serve, but you didn't need one in my day. You've got to have a serve to challenge for the top now.''
When Petra Kvitova won Wimbledon at 21 this summer, she was the first women's major singles finalist under 25 in a record seven straight majors. "Over the years,'' Jelena Jankovic said, "girls have become stronger and stronger. So fast. So fit.''
A former No. 1 without a major title, Jankovic is 26. Old enough, now.