Wimbledon: What the data says about some tennis myths

Do new balls help the player serving? And are you more likely to serve an ace at game point?
Venue: All England Club Events: June 27 – July 10
Cover: Live on BBC TV, radio and online with extensive coverage on BBC iPlayer, Red Button, Connected TVs and mobile app.

During the first set of the first game at Wimbledon next week, the commentator will invariably mention that the server will be using the “new balls”.

After the first seven games, and then every nine more, the old balls are removed and replaced with new ones. The popular belief is that the new, firmer balls give the server an instant advantage, something that will diminish game after game until they are replaced.

But is that true?

Dutch professors Franc Klaassen and Jan R. Magnus decided to find out if that was the case and set out to investigate as many tennis myths as possible.

“The list [of myths] was created by watching tennis on TV and listening to commentators,” explains Professor Klaassen. “And we combined it with our own many years of experience as tennis players.”

What followed was 25 years of research, academic papers and a book.

Initial work included data from 86,298 points played at Wimbledon and was expanded to well over 100,000 points played at other Grand Slam events, collecting data from the 1990s to the present.

So what did they find out and will it make us see the game differently?

The Myth: All points are equal

One of the fundamental questions that followed research from the 1970s was whether or not points are independent of each other.

Does the previous point affect the one played now?

The results were unequivocal and confirmed that not all points are equal, although the difference between them is small.

This information was coupled with the idea that an ace could be worth more than one point. The prevailing opinion was that serving an ace gave the server so much more confidence that they were more likely to win the next point.

The data showed that in men’s singles there was an effect and after an ace the server was more likely to win the following point since the ace was worth 1.04 points and in women’s singles the effect was worth 1.01 points.

These margins are small, but sometimes that’s enough to change the outcome of a point, and therefore a game, and ultimately a match.

The Myth: The seventh game of the set is the most important

If the points are not equal, what about games?

The professors knew that legendary BBC commentator Dan Maskell often said the seventh game of a set was the most important and whoever won it would most likely win the set.

That has been proven wrong, and that the most important games are numbers 11, 12 and 13 (tiebreak) if the set goes that far.

The seventh game could come with the scores 5-1, 4-2, 3-3, 2-4 or 1-5. One might think that the seventh game is important at 3-3, but the data shows that is not the case. In fact, the seventh game has less impact on the set than the sixth.

The professors developed an “importance” measure to rank each game from 1 to 100. Game six scored 43.0 in men’s singles and 41.3 in women’s singles, while game seven scored 37.6 in men’s singles and 36.6 in women’s singles.

The “importance” was the probability of the server winning the set in that game, given that he wins the game, minus the probability of the server winning the set, given that he loses the game.

The Myth: Players are likely to lose serve once they break their opponents

Klaassen and Magnus analyzed what happens at the “big points” and selected hold and play points to consider.

They found that in both men’s and women’s singles, the number of aces to game point increased, but so did the number of double faults.

The result was that the total points won on serve at the game point was slightly less than at all other points. Men’s servers won 62.2% of points at breakpoint compared to 65% of all points, while women’s servers won 53.5% of points at breakpoint compared to 56.4% of all points. .

When the game point is a match point or even a championship point, the stakes are obviously higher.

The raised aces and double faults at this point were never more tense than at the end of the 2001 final between Goran Ivanisevic and Pat Rafter. The high-serving Croatian led 8-7 in the fifth set, but served up two aces and three double faults at crucial moments before eventually claiming the crown in his fourth final.

At the break point, players serve fewer aces, are more careful to put the ball in play, and play more cautiously.

So a player who wins a break of serve relaxes and the player who just got broken tries extra hard to cause a break back to happen immediately?

The answer was no. Overall, a player is more likely to hold their own serve after taking a break.

Men have an 81.8% chance of holding serve, which increases to 83.3% after a pause. For women, it’s usually 64.3%, rising to 68.3% after a break.

men Women
Aces at game point 10.9% 4.2%
Aces on all points 9.1% 3.3%
Double fault at game point 5.7% 5.3%
Double faults at all points 5.5% 5%

The Myth: Whoever wins the fourth set will most likely win the fifth

Having previously looked at the impact of one point on the next, they looked at the impact of winning a game on the next.

Are the players getting into the swing of things, or what they called “winning spirit”?

This was the most surprising finding.

“The winning mood is much smaller than we thought,” explains Professor Klaassen. “Yes, there is momentum, good performances in the last few points signal that the player will also do well in the current moment. But that momentum is low.”

How would this translate to thinking that a player who wins a set to match and needs a crucial fifth (men) or third (women) set would have an advantage?

The data was split into seed and non-seed and gave clear results.

If two seeded players are playing, the winner of the fourth set will most likely lose the fifth (an 11.1% chance of the same player winning sets four and five).

But if two non-seedlings are playing, it’s the other way around, since the winner of the fourth most likely wins the fifth as well (a 60% chance that the same player will win sets four and five).

When a seedling plays a non-seedling, the winner of the fourth set is irrelevant since the seeded player has a greater chance of winning the last set no matter what happened before (an 80% chance that the seedling won sets four and five wins).

Those numbers are the same for women going into a third set.

Looking at the 20 men’s Wimbledon finals since the millennium, six have come the distance to five sets. In each set, the player who won the fourth set tied, then lost the fifth.

Twice Roger Federer triumphed in this way (in 2007 against Nadal and in 2009 against Roddick), but three times he lost (in 2008 against Nadal and in 2014 and 2019 against Djokovic).

The Myth: Serving new balls is an advantage

The data helps explain a lot about what’s happening in tennis, but what about the new balls?

Klaassen and Magnus found that with the new balls, slightly more aces were served by men (10% with new balls, 9.1% without), but there was also an increase in double faults (5.9% with new balls, 5.5 % without). ).

So the new balls go faster to produce the aces but are harder to control hence the double faults.

That’s not a simple answer, there are shades of gray. However, when the commenter reminds us that the server has the new balls, we know that more than usual “something” will happen.

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