First, I'm going to describe what I've done here and what incited me to do so. As we all know (I guess), tennis is more than than the statistics boxes that the WTA just gives to us match after match in other words tennis is much more than just plain winners
and unforced errors
. For facts, just check out the total points of any player in question it includes the forced errors yet, they never get referenced into the statistics boxes. So why this flaw !? Why make the statistics so "meaningless"
if all the components are not included !?
So that's where I took my curiosity into hand and wanted to know for Petra if her game ONLY consisted of hitting winners left and right so as a good amount of unforced errors, was her game only resumed to shotmaking or was she also good at constructing points, putting the opponent under pressure... without even hitting that much winners from the back and that's where this sheet came into mind.
I. Forced error - The notion of forced error, What is a forced error ?
A forced error is an error that was provoked by an opponent through good play... I don't know how to resume it any simpler but there's only one way to force errors from an opponent is through controlled aggression, point construction, moving her around the court, putting her into uncomfortable situations etc... that will have for result a forced error.
Let's take Petra, she doesn't forcefully need to move the ball around that much to generate forced errors... the simple fact that she puts so much pace into her shots, the placement are enough to have her opponent miss. She could still be hitting people off the court even if she would hit like 9 winners in a match depending on her opponent's abilities to control her shots or not.
From the numbers, we can observe that Petra's average winners are relatively close to the average errors she forces from her opponent, 28.93 to 26.19 - she relies on both capacities to hit you off the court and pressure you off the ground through aggressive play. Relating these 2 numbers, we can see that Petra wins an average of 54.81 points through just pure aggressive play (winners + forced errors) which is a great compromise.
II. Forced errors and the surface, the secret
People will be shocked if I said Petra forces more errors in her opponents than she actually hits winners on grass...
Kidding but actually it's close. Petra hits an average of 30.07 winners on grass and forces 30.47 errors from her opponents on the same surface. Observe now how this reduces from 30.07 to 27.2 and 30.47 to 26.2 on clay.
The explanation is pretty simple though it's the intrinsic characteristics of the surfaces in question. The reason for the high number of forced errors at Wimbledon is due to the simple fact that grass courts are quite fast. The ball bounces fast and low which makes it complicated for the player reaching it and returning it. The fact that Petra hits her shots so flat does also participate in the fact of all these forced errors. Rallies are generally short.
From my point of view, just my 2cts. interpretation, Petra could be hitting half less winners and with her tennis still blow off a vast majority of the girls off grass because her peak game on grass is very hard to handle as seen on the forced errors statistics.
III. From forced errors to the aggressive margin
So once we have a forced errors stats, we would like to know what is the margin of points Petra won through aggression... in fact we want to know how great is her shotmaking, IDK, it's just simple as that and what the aggressive margin represents. The aggressive margin can either be positive or negative which in the second case would mean that she wasn't abled to get things right on the court.
Petra's aggressive margin on grass averages 58.35 points which is 4 points over her overall average of 54.81 points with a peak at 71 in Wimbledon's 2010 QF. On clay, this falls at 45.8 simply because of the surface which doesn't allow her to be that much aggressive from the back court.
How does this interpret, +54.81 is just exceptional and a further confirmation for us to see how excellent her shotmaking is off the ground in both hitting clear winners and putting pressure on the opponent off the ground by forcing errors from them.
IV - Winning play, an unknown
Fans generally just watch her and are astonished at the tons of winners she hits during a given match... but let's be serious. Is she THAT good at first, taking a point into hand and second ending it with an aggressive play !? That's where this notion is enlightening.
An eventual warning, the winning play
does not factually exist to say so as a stat but just something I wanted to introduce to have in depth analyses of Petra and her game.
She average 18.69% in the winning play department, remember ? It means 18.69% of the times, Petra is abled to take control over a point and end it with an aggressive play (sounds like the aggressive margin or the forced error, no !?). On grass, this numbers goes up to 21.75% and up to 23.51% in Wimbledon 2011 so it shows that she still has a huge margin of progression in terms of ending points. Why !?
V. The winning play in comparison to the Unforced errors
The winning play on it's own doesn't have that much importance (from my point of view)... it takes depth in comparison with the unforced errors. Indeed, for every 18.69% of times Petra ends a point with an aggresive shot she hits 18.69% of UEs...
Let me show you why Petra's progression can greater, let's focus only on Wimbledon 2011. Compared to 2009, she reduced her UE count from 17.83 to 13.14 average, enormous considering that she hit much more winners in 2011, 33.28, almost 3 every 10 games. If we compare Petra before the SF stage in 2011 compared to 2009, she was 35.6 winners for 13.1 UE... no need to be a genius to see the outcome.
Let's go back to the overall stats, remember ? 18.69% of winning plays for 18.50% of unforced errors get the thing ? For every 6 aggressive shots (forced or clean winner), Petra hits almost as much UEs or close, 4 per 10 game, this is where she can progress and she did progress in Wimbledon 2011.
I know this is a lot to say quite a little but it was necessary for me, myself and I to make the factual demonstration to my spirit to observe what others said or hesitantly without any kind of solid base.
Stats are probably the most complicated thing to interpret. Petra's game is both very risky but also very productive of the ground from the amount of pressure she's abled to generate either with her quality of shots, height : flat, lift etc..., pace and placement. These numbers shows that she's clearly not only a shotmaker.
It is up to her opponent's, if they can't control her basic shots (rally balls or any ways the shots where she plays a little more patient yet still pressuring, looking...) then they're simply getting overpowered during the course of a match because of the pressure her game puts and there failures to take hold of that pressure.
She's always going to hit more winners than unforced errors that's normal but I think it's important to not get fooled because she also forces a lot of things from her opponents who become very uncomfortable, either having them go for too much (so more UEs for them), perhaps simply just have them miss because they're clearly lacking of time or basically can't control the very simple shots.
It's very important to note that Petra's opponents in majors do not hit lots of UEs. An average of 16.37 but she simply just doesn't allow them to anyways since she has total control over everything. She hits more UEs and more winners than her opponents and the only two times since 2009 a player hit more UEs than Petra hit winners was in Wimbledon 2010 vs. Cirstea 1st. round and AO 2011 1st. round vs. Sally Peers. In fact, her opponents UEs in majors only counts 36.14% of times in the outcome of her matches which means 63.86% of the rest of times she is the decider (clear winners, forced errors or just UEs herself).
The last fact to take into consideration is the UEs and that's where perhaps her game is always on the border line... just the right balance between aggression (forced or clear winners) and UEs and in Wimbledon 2011 it was clear -4.69 UEs in average is a huge cutdown while the winners took +5.95 in average.
It's unfortunate I can't do that for the WTA tour but hopefully my very small contribution will bring better light into the majors and her game.
Any complementary informations on these I stated above can be found in the ITF Technical, coaching section search for Seeking to Measure the Quality of Tennis Performance. - PDF