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View Full Version : A New Way to Think About Break Points

The Wreck
02-16-2012, 02:16 PM
Had some thoughts rattling around in my head while watching tennis the other day, and always been interested in statistics, so I made a quick blog (temporary, really) to house my thoughts for the time being. Thought I'd post it here and see what people thought and what suggestions you could provide. Thanks.

When watching a tennis match you’ve undoubtedly seen the statistic flashed on the screen: ‘Break Point %’, or something similar. That is, the amount of times a player converted a break point when they had a break point opportunity. You may even have seen the statistic, tracked over the course of a season, percentage of return games won. Successfully returning serve is arguably the most important part of winning in tennis, so it’s good that we have metrics that attempt to show return of serve prowess. Unfortunately the two statistics I’ve mentioned are inherently flawed and can often lead us to false conclusions.

Break point conversion rates sound like a good metric; how often did the player win an important break point when they had the chance. But this percentage on its own can often disguise what really happened. A player who has five break point opportunities and converts on two of them has a break point conversion rate of 40% (the average for most ATP players). But let’s say their opponent in that match had ten break point opportunities and converted on four them. Their percentage is also 40%, but they broke twice as many times. This is where I feel the statistic is flawed.

There may be a game where you get the score to 30-40 in your favor, win the next point, and your break point conversion rate is 100%. Or you could have a game where you go to several deuces, back and forth, and finally convert on your fourth break point opportunity in that game. Your conversion rate is 25%. Why should we care how many tries it took you to break as long as you do actually break serve in the end? The end result is the same. While it’s true a better returner may convert within that one game on fewer opportunities, it’s irrelevant really. You don’t get bonus points in tennis for being efficient.

Percentage of return games won aims to correct for some of the shortcomings of the previous statistic. You get the frequency with which someone breaks and nothing else. Sounds pretty good. As far as measuring just returning ability this statistic works fairly well. But when evaluating a player as a whole, it too can mislead. Say you’re on serve with your opponent at 3-3. You get a break and go up 4-3, but on your very next service game you’re broken back and the score is again tied, 4-4. Yes, you broke your opponent so your percentage of return games won increases. But you were immediately broken back which negated your great return game entirely. A break is only useful if you keep the advantage. So sure, it’d be great to have 50% of return games won, but if you are immediately broken back half those times, you’re not getting ahead of your opponents very often.

With that being said, I’ve created what I think is a more comprehensive (though not perfect) statistic called Effective Break Percentage (or Proportion), or as I’ll refer to it, EBP. The formula for the statistic is as follows:

(Breaks – Breakbacks) / (Games with Break Chances)

That is, the number of games in which the player successfully broke their opponent’s serve less the games in which they were immediately broken back (excluding times when serve was broken to win the set). That number is then divided by the number of games in which the player had at least one break point opportunity. To further clarify: over the course of a match you have break point chances in 8 games, you actually break in 3 of them, and after one of those games your opponent immediately broke you back. Your Effective Break Percentage for that match is ((3-1)/8 ) or 2/8 or 25%.

This statistic isn’t entirely without faults. In percentage form, you still face the issue of 1 out of 4 being treated the same as 3 out of 12. So when looking at an individual match, I believe it’s better to leave it as a proportion. Over the course of an entire season though, the amount of games should be high enough to more accurately show who’s more proficient at earning and keeping breaks. I’m open to suggestions on how to account for the discrepancy in individual matches, though.

It’s also a difficult stat to actually compute. You can’t really retroactively go and calculate this percentage without point-by-point breakdowns of matches, which are only available for majors, as far as I know. So unless the Tennis Channel decided to adopt this idea, you’ll have to carefully track the points when watching a match.

So why bother? Well, break points have been considered by many to be the most important statistic to focus on in determining the winner of a match. Research has been done to show that that may not actually be the case. I’m not convinced entirely, though. In the future I’d like to test the predictive power of EBP and see if it explains wins any more than break point conversion does.

What’re your thoughts? Is it a useful statistic worth tracking or just as unreliable as break point conversion? As mentioned, any suggestions on how to improve this is much appreciated, and hopefully I can work with the data further in the future.

http://tennismetrics.wordpress.com/

kragster
02-16-2012, 02:33 PM
OP you have some interesting thoughts here. I think your system is great but would end up being somewhat complicated to implement. It did get me thinking though, a simple adjustment from the current system would go a long way - When counting breakpoints, only count 1 breakpoint per game. So if you have a long game that goes back and forth from deuce 20 times, that should only count as 1 breakpoint.

I think this will give a better sense of how many opportunities a player had. If you see someone lose a match with stats like 1 on 20 conversion, you would think that the player had a lot of chances. If those were all in 1 game though, this would be somewhat misleading as really the player had only 1 game that he could have broken.

What we need is distinct game break pt conversion i.e. only 1 breakpoint counted per game in which you had breakpoint opportunities.The one flaw with this system though is that it would not be a good judge of situations when a player choked i.e. those cases when a player has multiple breakpoints in the same game but doesn't even convert one.

Maybe they should have a breakpoint conversion along with a breakgame conversion. That would give us the complete picture.

Raz11
02-16-2012, 02:56 PM
OP you have some interesting thoughts here. I think your system is great but would end up being somewhat complicated to implement. It did get me thinking though, a simple adjustment from the current system would go a long way - When counting breakpoints, only count 1 breakpoint per game. So if you have a long game that goes back and forth from deuce 20 times, that should only count as 1 breakpoint.

I think this will give a better sense of how many opportunities a player had. If you see someone lose a match with stats like 1 on 20 conversion, you would think that the player had a lot of chances. If those were all in 1 game though, this would be somewhat misleading as really the player had only 1 game that he could have broken.

What we need is distinct game break pt conversion i.e. only 1 breakpoint counted per game in which you had breakpoint opportunities.The one flaw with this system though is that it would not be a good judge of situations when a player choked i.e. those cases when a player has multiple breakpoints in the same game but doesn't even convert one.

Maybe they should have a breakpoint conversion along with a breakgame conversion. That would give us the complete picture.

Agreed. Simple and effective if we use both stats.

OP, you do have an interesting stat which is effective but can be a bit complicated. Especially for the casual fans, they would have a hard time understanding this.

The Wreck
02-16-2012, 03:08 PM
Agreed. Simple and effective if we use both stats.

OP, you do have an interesting stat which is effective but can be a bit complicated. Especially for the casual fans, they would have a hard time understanding this.

Understood. It's not practical the way tennis stats are tracked nowadays. As far as the casual fan understanding it, I would hope that it'd be like OPS in baseball. Most people have no idea what OPS is or how its calculated, but they know a higher one usually means a better hitter. Same here. One of my goals (which I havent been able to test yet), is to see how this EBP related to wins (does the higher EBP win 99% of the time, etc.)

Raz11
02-16-2012, 03:59 PM
Understood. It's not practical the way tennis stats are tracked nowadays. As far as the casual fan understanding it, I would hope that it'd be like OPS in baseball. Most people have no idea what OPS is or how its calculated, but they know a higher one usually means a better hitter. Same here. One of my goals (which I havent been able to test yet), is to see how this EBP related to wins (does the higher EBP win 99% of the time, etc.)

Theoretically it should work but how would it incorporate tie breaks. Cause some matches are determined by tiebreaks and not breaking of service games.

Example:
Set1:
Player 1 breaks Player 2 but gets broken back. Later breaks again and wins the set.
Set2:
Player 2 breaks Player 1 but gets broken back. Later breaks again and wins the set.
Set3:
Player 1 beats Player 2 in the tie break.

Player 1 had 3 breaks and 1 break back. Same for player 2 but player 1 had more chances.

The EBP if my calculations are correct then player 2 will have the higher EBP but lost the match in the end.

Sentinel
02-16-2012, 07:43 PM
I've always wondered this abt the BP conversion stats (If you had a triple BP and converted on the first it would be 100% right, but then when they show 5 of 8 converted then ...)

How about counting BP's missed rather than converted ?

In the above case you have 0/3 BP's missed. I know this seems to be confusing too, doesn't tell you how many times you did convert when you add them up and have say 5/15 missed. So how many times did you break ?

sbengte
02-16-2012, 07:58 PM
Maybe they should have a breakpoint conversion along with a breakgame conversion. That would give us the complete picture.

I agree that it is more meaningful to look at these two stats together than just BP conversion.

Have there been instances when a player has won more points on return than the opponent and still broke the opponent fewer times (and lost the match) ?
Does it make sense to look at a stat like
(total points won on return Vs break point conversions) ?

I guess in some way, that stat would be a measure of how well the player played the big points as compared to overall points. Similarly you can look at points won on serve in relation to break points saved. (Again a measure of how well you served on the big points).

It would be interesting to look at this stat in some of the Fedal matches (from before 2008 ) where Fed typically would create a lot of break opportunities but not convert them.

rosewall4ever
02-16-2012, 09:23 PM
breakgame will only be useful if it it indicated when the break happened and who in the set served first. a breakgame is evident from set score...

Fate Archer
02-17-2012, 03:07 AM
breakgame will only be useful if it it indicated when the break happened and who in the set served first. a breakgame is evident from set score...

If I'm understanding this right, the breakgame could be useful, as discussed already, to accurately show how many opportunties a player had in the match, without being overly inflated by the times a player didn't convert a breakpoint in a single game.

We could have a situation where the score is leveled at 4-4, but while player A held easily in all his games, player B faced multiple breakpoints in all his service games.

The breakgame percentage would be 0% (0/4) still, like in the breakpoint conversion (which could be as high on breakpoints missed as say, 0/12), but it would more accurately translate how much a player capitalised or not on his opportunities through the course of a match.

To put it simply, it would indicate how many games you won when you had breakpoints. This may not be implied in the score (two situations where it may not: 1- as in the above instance, a break does not happen. 2 - the other player breaks back to even up the score. In this last case the OP's metric which accounts breaks back may show a bit more insight).

I agree that both stats (breakpoint and breakgame) are complementary to each other, and the use of the breakgame scout could prevent situations where the breakpoint conversion alone would be totally misleading, such as a match where the breakpoint conversion was 9% (1/11 chances), but all those breakpoints came in a single game and thus there was only a single break in this match. It could well happen.

In addition, it would be so much easier interpreting a match through the statistics using these stats coupled, let's take this last example, we can gather that given that the match was decided by a single break, it was all pretty even until this very important game was played, where it took 11 chances for the break to happen and the match to be decided.

TL;DR: Broadcasters should definitely include the breakgame stat on their statistics when showing breakpoint conversions. It can be extremely misleading showing one without the other.

sureshs
02-17-2012, 05:38 AM
What happened to Breakpoint?

double barrels
02-17-2012, 12:21 PM
schemathematics....love it

dominikk1985
02-17-2012, 12:49 PM
this is like in baseball. everybody loves clutch hitting but statistics show that clutch is basically ********.

the guy who has more breakpoints usually wins. and in baseball the guy who hits better will usually hit better with RISP.

also the teams who GIDP the most usually score the most runs. of course GIDP is bad but usually it is just an indication of having a runner on first often which means a lot of runs.