Need for speed and bounce: explaining why balls count big time in sport

Novak Djokovic hit his way to double-digits last night, securing a 10th Australian Open title, a record-levelling 22 major titles, and a return to the world leaderboard. All that with what he described as “fluffier” and “bigger” balls.

Djokovic was among several top-seed players during the 2023 tournament to serve Tennis Australia a below-average review of its match ball of choice, declaring the Dunlop flat, fuzzy and unfeasible to hit winners. The balls were said to have a shorter-than-short lifespan that protracted play by lending themselves to slower strokes and longer rallies.

As tennis allegedly turns half-speed, other ball sports are migrating to makes and models that shave match time off the clock.

Former Australian table tennis player Paul Pinkewich says the official shift from 40mm celluloid balls to 40 plus plastic balls (a decision made by the International Table Tennis Federation in 2014) has almost a decade later proved detrimental to the game.

“I’m a defensive player. With the old celluloid balls, I could get heavy topspin, with plastic balls it’s all power. People are just belting the crap out of them. You’ve got to be Spider-Man to get the ball back,” Pinkewich tells Crikey.

Where players used to stand six to seven metres behind the table and play a highly tactical game, Pinkewich says it’s now up close and personal, with rallies regressing from skilled back and forward to a smack exchange with a hit rate that can’t even fill the fingers on a single hand.

“Nowadays they’re all attackers and they’re all playing the same. They do a big serve and then it’s bang. You have no hope of returning it,” he says.

“I’ve played for Australia 287 times and I can’t watch these top-level players play any more. Bang, bang, bang, end of rally.”

The International Table Tennis Federation (ITTF) had put the ball change down to cost, resource availability, and safety — the flammability of celluloid makes it difficult to ship — and acknowledged that it would undoubtedly invoke fierce resistance. There was deep division between the “optimists” in favour of change, the “pessimists” who resisted change, and the cohort of “indifferent”.

The pace of plastic v the creative power of celluloid is a uniquely ping-pong phenomenon, but the psyche of spheres exists right across the sporting spectrum. Be it material composition, level of squish or degree of bounce, the balls are not benevolent beings.

It’s what University of Michigan professor of materials science and engineering and author of Corked: Tales of Advantage in Sports Brian Love calls “controlled advantage” and explains why some athletes go to such great lengths to (illegally) tamper and toy with match balls.

Basketball has a long history of deliberately deflated balls (players would carry pins and prick the ball mid-match). It’s a similar story in the NFL with the “Deflategate” scandal. Cricket players tried their hand with sandpaper to wear the red rocks down. And the list goes on.

So how much is in a bit of bounce?

The hop, skip and jump of a ball is calculated using the “coefficient of restitution”, a measurement that weighs up the profile of a ball with the surface it strikes. Both affect the level of bounce (hence the difference on grass v clay tennis courts).

For a tennis ball, there are layers of structures that can make or break performance. There’s felt weave (a combination of woven and unwoven fabrics — wools, nylons, and polyester), rubber sealants and post-production primping and priming for aesthetic purposes.

Put together, Love explains that Dunlop is effectively buying felt, punching out a “dog bone-like structure” and laminating this together on the rubber ball.

“If it’s not a materials selection problem, there is a felt-raising step done after manufacturing to tease the felt into a fuzzier state. That makes it more likely to be sloughed off when hit,” he says.

But elite players strike the ball with more force than your average Joe, and Love explains there is also the possibility that high compressive pressure hits home with small amounts of air leaking from the rubber core. This is, however, something that can be fixed with filler — silicone injected into the rubber frame — at the point of manufacturing.

So why don’t ball sports lean into the creation of longer-lasting balls? Simple, says Love. They want quick hits and returns with audiences: “Analytics has moved to a point where people don’t have time to watch a three-hour baseball game. They want a five-minute episode that accurately describes the change in momentum throughout the game.”

Love heralds tennis as a bit of a last man standing for ball sports, with manufacturers retaining independence from the sports organising body (Dunlop is contracted by Tennis Australia). Compare this with baseball, for example, where the governing body owns the ball manufacturer and therefore has full jurisdiction over look, feel and behaviour.  

“I can only assume that in the interests of trying to make baseball more exciting, they’re directing balls to be made in certain ways,” he says.

So is tennis headed the same way?

There are growing calls to cut court time — particularly in response to external factors like heat and humidity — and Love says faster balls are one option to help make those ends meet. But he points out that tennis is a back-and-forward game and therefore ball advantage is not as simple as game, set, match.

Tennis Australia has renewed its contract with Dunlop for a further five years.