I just can’t stop thinking about this Ben Rothenberg piece, aptly titled “Unforced Error Is Unloved Statistic Among Tennis Players“. You probably read it already — it came out during the first week of Indian Wells. If you haven’t, do take a look. Rothenberg tells the story of how this particular statistic came to be, and he has quotes from Andy Murray, Sam Sumyk (Azarenka’s coach), Kevin Fischer (senior communications manager for the WTA) and Roger Federer about these pesky unforced errors, as well as statistics in general. Here you have three of these quotes:
“I think if you have two or three different people recording unforced errors, you’re going to get two or three different figures.” – Kevin Fisher
“I’m not interested on the statistics, because I’m not sure it’s accurate.” – Sam Sumyk
“The forced error, unforced error count is always extremely tricky.” – Roger Federer
I was not surprised when I read this, but it did amuse me. Why so much resistance towards a statistic that is so basic? Sure, we can all agree that a large part of the unforced errors in a match is attributed in a subjective way. The obvious exception is the double fault, which is the lone objective element of the unforced error count. However, after years of watching tennis, it doesn’t seem to me that an unforced error is such a mysterious thing as to generate this much skepticism among some of the pros. I’d probably argue that if you have 100 passionate tennis fans tallying the unforced errors of a random match, they would probably do a good job determining what is an unforced error and what isn’t (provided the match doesn’t involved their favorite player, naturally).
Anyway, since I don’t have the funds to have 100 people tally unforced errors, I decided to run a little experiment on my own. During today’s match between Sorana Cirstea and Angelique Kerber, I tallied the unforced errors myself. In addition, I could take advantage of the new live stats provided by TennisTV during their streaming of Masters 1000 events, which even break down the unforced errors by whether it was a forehand or backhand mistake. Looking at those numbers will help zero in on where the discrepancies lie at the end of the match.
What is my hypothesis going into this experiment? That any difference between my tally and the official tally will be minimal, if any.
Without further ado, here is what transpired in the first set, which Cirstea won 6-4 (the blue highlight on game number three means that Kerber broke serve in that game, and the red highlights on games six and 10 mean that Cirstea broke serve in both of those games):
As you can see, I tallied 13 unforced errors for Kerber, and 14 for Cirstea. Here is the official tally from TennisTV:
Notice that TennisTV gave Kerber one more unforced error than I did, while they assigned Cirstea two more unforced errors. Regarding the latter, I can guess where at least one of these came from: in one of the first games of the match, Cirstea hit a smash into the net. I gave her a pass on it, since it wasn’t a straighforward smash — Cirstea had to backpedal a bit to hit it. However, I can see how that can be tallied as an unforced error.
Now for an important disclaimer: using TennisTV’s nice new controls that allow you to go back (or spring forward) 10 seconds in a match, I was able to review several points to see if I got it right. Naturally, the folks tallying the stats live don’t have that luxury. Huge advantage for me.
Anyway, let’s move on to the second set, which Cirstea won 6-0 (the red highlights on games two, four and six just mean that Cirstea broke serve in those games):
And here is my final tally:
The broadcast didn’t produce a segregated second set graph, but they did produce a final stats graph:
Notice that my tally is only off by one unforced error for each player. That’s not bad, right? Now let’s see what the live TennisTV stats (the ones only users can see and are not part of the broadcast, though they come from the same source). The red highlights are mine:
Notice that I actually have the same numbers as the Tennis TV crew for forehand unforced errors for both players. The official tally gave Kerber an extra backhand unforced error, while it seems like I gave Cirstea one backhand error too many. Notice that the two overhead smashes Cirstea missed have not been tallied as either forehand or backhand unforced errors. I judged that only one was an unforced error and tallied it as a forehand unforced error.
Regardless, you can clearly see that the difference between tallies is tiny.
As expected, there was a variance, but it was quite minimal. Hence .. .why the resistance to a statistic that could be very useful — if not for players, for coaches? Is it because the nature of the stat, which illustrates an error, a mistake, something that shouldn’t have happened, might affect the psychological state of a player? I can see that. Tennis is such a mental game, and it’s not like you can sub someone in if a player is having a horrific day with unforced errors (as it happens in basketball when a certain player commits way too many turnovers or misses way too many shots). Also, focusing on errors might erode a player’s confidence.
However, wouldn’t you want to see these numbers as a coach? I keep thinking of the Indian Wells matches between Juan Martín del Potro and Andy Murray, and then the semifinal between Del Potro and Djokovic. In both of those cases, the higher ranked men had an inordinate amount of unforced errors on their backhand side, which is the bedrock on which their baseline game is built on. Wouldn’t Marian Vajda want to know this information, so that he can later watch the match again and try to figure out what happened during all those backhand unforced errors?
The unforced error stat is not a solution to anything. We can all agree on that. But it is a handy tool to figure out if a player is struggling with a particular shot. Then you can start asking why that is happening: it could be that the player is not moving their feet, that they took their eyes off the ball, that they didn’t put enough spin on the shot, etc. That’s for the coach to assess, but it’s sometimes visible to anybody who’s watching the match, too.
As viewers, it’s always fascinating to see the winner/unforced error count. It usually tells you something about how the match went. There’s the famous example of the 2007 Australian Open semifinal between Fernando González and Tommy Haas, which I wrote about here. In that match, González was credited with 42 winners and just three unforced errors. You might have heard that the Australian Open has a reputation of being kind with the unforced error count. As I watched that semifinal again, I paid close attention to the unforced errors, and the official tally was indeed off … by just two. Fernando González committed five unforced errors (all in the second set, amazingly) in the entire match. And had 42 winners. That tells you all you need to know about how well González played.
In the same vein, you can see just how good Sorana Cirstea was in that second set today: the official tally had her committing only one unforced error, while I had her committing only two. Either way you look at it, Cirstea’s play was remarkable.
Regardless, the main lesson here is that when you see those unforced error counts on your broadcasts, or when you use TennisTV, you can be reasonably confident that they are a fairly close reflection of what is happening on a tennis court. Looking at the numbers might lead you to identify certain trends, as well as to ask many questions.
And that’s the best part of any statistical analysis, no?