Tennis is literally getting bigger.

The 2017 Wimbledon final saw a 6’ tall player top a player who stands 6’1” … on the women’s half of the draw. (Garbine Muguruza beat Venus William in straight sets.) On the men’s side, it was really big. 6’1” Roger Federer wound up on top, but he had to face 6’5” Tomáš Berdych in the semifinals and 6’6” Marin Čilić in the final. The other semifinalist, Sam Querrey, is 6’6” too.

Three reasonably sized men have dominated tennis in recent years: Federer, 6’1” Rafael Nadal and 6’2” Novak Djokovic. They have a won a staggering 46 Grand Slam tournaments between them. (Since 2006, everyone else in men’s tennis combined for just eight.) Of course, 5’9” Serena Williams has been the unquestioned queen on the women’s side with her 23.

But even these greats will have to move aside one day. All four are over 30, with Federer the oldest at 36. Djokovic had season-ending elbow surgery. Williams is soon to be a mother.

Clearly, a new order is coming. Brad Gilbert suggests the members of it will likely be huge, telling RealClearLife: “I think there’s a lot better possibility of being really good at 6’9” or 6’10” than being really good at 5’7”.”

As a player, Gilbert reached #4 in the world. He went on to coach players including Andre Agassi (who, in case, you’re wondering, is 5’11”) and serves as a tennis analyst for ESPN.

“When you’re tall, it’s about your movement,” Gilbert said. And increasingly, tennis is filling up with just that, tall folks who can move.

Height has always presented certain advantages in tennis, notably the ability to hit faster serves. Yet it was argued that there were also drawbacks, with a belief that (as the New York Times put it in 2003) the “quick stop-and-start movements and unusual body extension work to the disadvantage of bigger players, especially in the lower back and knees.”

John Isner was in many ways the stereotypical tennis giant. Standing 6’10”, he is renowned for his ability to boom serves at over 150 mph. He’s most famous for winning the longest match in tennis history at Wimbledon, triumphing over Nicolas Mahut in just over 11 hours: 6-4, 3-6, 6-7 (7), 7-6 (3), 70-68. (Yes, there were 138 games played in the fifth set, due to the absence of tie-breakers.) Isner’s serve made the difference in the epic match, as he held serve in an absurd 89 of 90 service games, facing only three break points total. It brought him a brief-but-intense moment of celebrity.

The rest of Isner’s game never equaled that sublime serve. (Holding serve for 69 straight games in the fifth set is remarkable, but it only happened because he failed to break Mahut’s serve for 68 straight games.) While Isner cracked the top 10 in the rankings for a time, he has only reached the quarters of a Grand Slam tournament once, way back in 2011. He seemed to prove that, in tennis at least, with length came limitations.

Of course, it was once believed that no one 6’9” could play point guard in the NBA. Then Magic Johnson arrived.

“If you’re athletic, you have skills, then height is an advantage,” said Gilbert. He noted that young players of all sizes should work to develop their footwork by doing “anything you can do to help you with your movement. A lot of Europeans play soccer.”

(Yes, the football fanatics include the Swiss Federer, the Serb Djokovic and the Spaniard Nadal—the video below does not lie: Rafa has skills.)

Tennis, like many sports, has seen athletes get bigger over the decades. Between 1960 and 1969, 5’8” Rod Laver won 11 Grand Slam tournaments and another eight Pro Slam finals. These are remarkable totals, but they would have been even more impressive if he hadn’t lost seven finals to 5’7” Ken Rosewall.

Whereas it was frequently noted how opponents seemed to tower over 1989 French Open champ Michael Chang, who still could have looked down on both Rod and Ken at 5’9”.

To get a sense of how player heights have changed, compare Laver to Federer in the photo below.

Rod Laver and Roger Federer at the unveiling of the Laver Cup trophy at Wimbledon on June 29, 2017. (Clive Brunskill/Getty Images)

Federer is five inches taller than Laver, just as 6’6” Juan Martin del Potro is five inches taller than him. Del Potro knocked off Nadal in straight sets and then ended Federer’s run of five straight titles to take the 2009 US Open, a victory that seemed to signal the super-sizing of tennis. However, del Potro has yet to win another Grand Slam as injuries derailed him, causing him to miss 13 majors since his lone triumph.

Gilbert dismissed del Potro’s setbacks as proving the big are at greater risk for injury: “When Kevin Durant gets hurt, do we say it’s because he’s tall? Injuries happen in sports.” (It should be noted del Potro’s biggest health issues have stemmed from body parts that shouldn’t be particularly impacted by height: his wrists.)

Indeed, Gilbert predicted, “I think we’re headed for our first 6’6” guy to be #1 in the world.”

He even has the candidate: Germany’s Alexander Zverev. Number seven in the world (and rising) at just 20, Zverev confirmed he’s a force with a Rogers Cup final victory over Federer.

Roger Federer and 6’6″ Alexander Zverev at the Gerry Weber Open 2017 in Halle, Germany on June 25, 2017. (Franziska Krug/Getty Images for Gerry Weber)

“He has that great wingspan on the return of serve,” Gilbert said. “And he moves … Unbelievable. He’s the perfect 6’6” the way he moves, and he’s athletic, he’d be like a wing guard in the NBA.”

Those with children with amazing groundstrokes but an ancestry of decidedly average height, don’t lose hope: both men and women’s tennis have a factor that should limit the numbers of Goliaths.

On the men’s side, the force that should keep tennis from getting too gigantic is the NBA.

Gilbert noted that tennis isn’t necessarily the most appealing sport for kids: “It takes a parent or a coach to take you to tournaments. It’s expensive.” Not to mention: “You don’t have teammates. You’re going to be on your own. That’s the greatness of it. That’s the toughness of it.”

The result is that it’s not surprising if a player with the size and athleticism of a Zverev chooses the courts favored by his countryman Dirk Nowitzki and plays basketball.

But while players in the NBA earn seven or eight figure sums each season, the women good enough for the WNBA can expect to make about 50 grand. (Better paydays are available overseas.)

Serena has earned over $84 million in career prize money, not counting endorsements.

And suddenly it makes sense for parents to urge their little girls to pick up rackets.

“On the women’s side there’s no doubt in my mind they’re getting the best athletes in the world because women’s tennis is the biggest sport in the world by far with women,” declared Gilbert.

Yet here too, there seems at least some room for those lacking the stature of a supermodel. Possibly because some people are so athletic they’re terrifying at any size, Gilbert noted, “There’s some smaller women who are more successful in women’s tennis.”

Don’t misunderstand: there’s still a lot of height, such as #1 ranked 6’1” Karolina Pliskova. But there’s also room for Simona Halep, who’s 5’6” and has twice reached the French Open final. Then again, a glass ceiling for smaller players may have already arrived: Halep’s been competing in Grand Slams since 2010 and has yet to actually win one.

Ultimately, Gilbert said there’s one rule that consistently holds true: “If you’re slow, that’s an obstacle at any size.”

Behold the mighty Zverev facing Federer in the clip below. (Bonus perk: you can discover how to pronounce his name correctly.)