Monday, August 27, 2007

How to make sense of the new WTA Power Index

In this post, I’ll take a short break from our ongoing discussion about how to improve your court movement to discuss an interesting speed-related event from the tennis world.

The event I wanted to mention was the launch of the “WTA Power Index” earlier this month at the final Acura Classic in San Diego. The point of the WTA Power Index is marketing—i.e. to give the fans a greater appreciation of the performance capabilities of the top female pros by highlighting how powerfully they strike the ball.

According to the official WTA Tour press release (8/8/07) explaining the Power Index:

“(I)t’s a great way (The Power Index) to recognize the extraordinary talent, athleticism, and sheer power of our top players… Other leading professional sports have introduced new methods to measure and compare the performance of their players to provide another level of insight to fans. The Power Index affords that same opportunity for women’s tennis.”

The WTA Power Index is calculated by taking the average speed of a player’s first serve, second serve, forehand, backhand, and overhead measured using the Hawk-Eye line-calling systems that are installed on all of the center courts of all the US Open Series tournaments.

And thus far, the most powerful player on the WTA Tour after the first three weeks of the Power Index is: (fanfare, please) Yaroslava Shvedova of Russia with an index of 102.9 MPH. Future Hall-of-Famer Venus Williams is second with an index of 98.8 MPH. Other notable (i.e. recognizable) names among the Top 10 players on the cumulative Power Index stats are Nadia Petrova (#4 at 97.4 MPH) and Elena Dementieva (#5 at 95.8 MPH).

Yaroslava Shvedova is the most powerful player on the WTA Tour? Hmmm… Shvedova isn't exactly a household name in women's tennis. She's not even one of the higher-ranked WTA players sitting currently at #74 in the official WTA Tour singles rankings.

In fact, there isn’t much of a correlation between the Power Index rankings and the actual WTA rankings. Look, the most powerful player in the short history of the Power Index, Shvedova, is currently ranked #74, and upon closer examination, 7 of the current Top 10 players on the Power Index are ranked outside the Top 25 of the actual player rankings.

I wonder how the WTA Tour is going to explain the inverse correlation between power performance and ranking performance?

Regardless of the Tour’s spin on the issue, I think that it shouldn’t surprise anyone that pure power isn’t necessarily a guarantee of match wins, especially among the women. Especially when you begin to notice that many of the biggest hitters among the WTA pros are not very adept movers on the court.

If you’ve been following this blog on a regular basis, you should understand by this point that slow court movement combined with big hitting is really a recipe for disaster from a high-performance perspective. Attempting to hit “big” with slow feet (you should also realize that there are many in the (pro) coaching establishment who preach that powerful stroking compensates for being a slow mover) is the classic, proven formula for maximizing unforced errors and makes it even more difficult to win any tennis match, especially one at the pro level.

Another detail to consider in explaining the disparity in the Power Index and actual player rankings is the fact that the women achieve those shot velocities with using far less (top-)spin that is essential to control such high-velocity strokes during play.

What this means is that while some WTA players may generate high shot speeds, they do so with far less control than their male counterparts on the ATP Tour. With far less spin on their shots (as in 50 to 70 percent less spin compared with the men on average) and therefore, far less control over their shots, the players who are top-ranked on the Power Index are, not surprisingly, also those same players with a proven reputation for generating large numbers of unforced errors during their matches.

Any tennis player who commits too many errors of the unforced variety is going to have a tougher time winning matches with any consistency. So when you begin to look at things more closely, it’s no real surprise that there isn’t a strong correlation between the Power Index rankings and the actual WTA rankings. The big hitters make way more errors during play and have a harder time winning matches consistently, so their rankings are lower.

I would be very interested to know what would happen if the WTA Tour could somehow introduce a “spin factor” into the Power Index—my prediction is that when spin production is part of the formula, the Power Index rankings will much more closely resemble the player rankings. And, yes, if you are wondering, with Hawk-Eye technology, it is possible to measure the spin rates of each shot struck during play.

Finally, I’ll make one final comment about the potential impact of the WTA Power Index… That is to say that tennis may be the one professional sport where the fans may achieve a greater insight into the quantitative aspects of the performance of their favorite players before the professional coaches who are paid the big bucks to train and prepare them.

Pro tennis coaches, by and large, do not pay much, if any attention to the quantitative aspects of the sport they are considered experts at. Sure they can recognize unusual physical ability—“talent”—when they see it, but they have almost absolutely zero idea about the quantitative details of the talent they observe.

Pro coaches generally do not know the speeds and spin rates or running times of their players. They consider these parameters to be unnecessary details mainly because they generally believe that the success in pro tennis is determined primarily, if not exclusively, by intangible factors such as “confidence” and mental toughness and motivation to perform hard work. They even believe that these intangibles can overcome the great majority of physical or technical shortcomings that a given player may have.

These beliefs are mainly based in the personal experiences of the great majority of coaches at the pro level, who were often former professional players themselves (with varying degrees of success). In the days when they were active players (typically in the 1970s and early 1980s), it was true that the psychological intangibles were paramount in determining a player’s ability to succeed on the tour because there was very little physical or technical separation between the pro players of that day and age.

Today, physical ability plays a far greater role in determining a player’s ability to succeed at the pro level, although the establishment continues to recite their deeply entrenched perception that the intangibles remain the most critical determinant of pro success. Today, racket speed and foot speed in particular create separation between the true pro contenders from the rest of those players toiling in the purgatory known as the Challenger and Futures circuits.

No matter how mentally tough and focused a prospective pro player may be, if he can’t consistently hit first serves over 125 MPH or can’t put a 130 MPH serve consistently back into play or retrieve a 95 MPH groundstroke slammed into the corners, no amount of mental skill and savvy can compensate for a lack of physical capacity.

This is the new reality of professional tennis…

Pro tennis has become essentially identical to other professional sports in that you must possess ultimate physical talent to succeed at the highest possible levels of the sport. Intangibles such as confidence and motivation remain as key factors in maximizing one’s competitive potential, but such intangibles can no longer compensate for a player’s physical shortcomings and athletic limitations (see Hingis, Martina).


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