Sunday, June 7, 2015

Why Nadal leads H2H stats

Although chatter on the topic has died down during Rafael Nadal's slump, there is still a significant fraction of tennis fans and analysts that believe that the Spaniard is the greatest tennis player of all time. And the favorite stat of every believer that Nadal is the GOAT has something to do with his head-to-head record against other top players.

There are several variations of the stat, but the one I want to look at is the one that is: Nadal has a winning record against each of the other three members of the Big Four.

Srinivas Murty (@jurasick) did a beautiful job of explaining this stat away with a tweet that said "Nadal titles by surface tells the tale of why he's so far ahead against rest of big 4 (16 hard, 46 clay, 3 grass)."

The tweet drew a negative reaction from the few fans of Novak Djokovic that saw the tweet, and I don't know which player Murty supports or what claim about GOAT he was trying to make with the tweet. However, the stat he shares in his tweet is the exact stat that kills Nadal's case for being the GOAT.

Yes, Nadal is great on all surfaces. That's how he won the Career Grand Slam. However, there is no denying that Nadal is far better on clay than the other two surfaces. Speaking comparatively, hard courts and grass courts are a weakness for Nadal. This fact is illustrated perfectly in Murty's stat.

So what does that have to do with head-to-head records? Let's look at head-to-head records based on a surface-by-surface breakdown.

Hard: 7-14
Grass: 2-1
Clay: 14-6

Hard: 9-6
Grass: 1-2
Clay: 13-2

Hard: 6-5
Grass: 3-0
Clay: 6-1

Nadal-Rest of Big 4
Hard: 22-25
Grass: 6-3
Clay: 33-9

Those are dominant numbers no matter which way you split it, but are those numbers really strong enough to make the case that Nadal is the GOAT. The answer is most certainly a no.

On the ATP World Tour, there are 14 key events, which are the four grand slams, year-end finals, and nine Masters series events. Of these 14 events, one (7.1%) is on grass, four (28.6%) are on clay , and nine (64.3%) are on hard courts.

I include those percentages, so that we can see how often we would expect the Big Four to meet on each of the three surfaces. However, the amount Nadal meets the other players on these surfaces is dramatically skewed. 

He has met Djokovic, Federer, and Murray on grass courts 9.2% of the time, which is just about right. However, he has met them on clay 42.9% of the time, which is much higher than expected. Also, only 48.0% of his meetings with them come on hard courts.

That is a massive advantage for Nadal to have met his biggest rivals a disproportionate amount of times on his favorite surface, while dodging them on the other surfaces, particularly hard courts. That pretty much explains away the entire head-to-head stat.

So why does this phenomenon occur? Because the Big Four has been so dominant in the last decade, each of the four of them have remained seeded very high at each of the 14 main tournaments that they play. Thus, they never meet in the early rounds of tournaments, rarely clashing before the semifinals and never before the quarterfinals. Because of that, they must reach the semifinals of a tournament to play against another member of the Big Four.

Well on clay, Nadal is reaching the penultimate round almost every time, meaning more meetings with the Big Four on clay. However, on hard courts, he doesn't run into the top players nearly as often, because he is not getting deep enough in tournaments as consistently as he does on clay.

So what would happen if they did meet a proportionate number of times on each surface? Let's look at what the Djokovic-Nadal head-to-head would be if they had a proportionate amount of meetings on each surface.

Hard: 9.43-18.86
Grass: 2.10 -1.05
Clay: 8.80-3.77

With these numbers, Djokovic leads the overall head-to-head 23.68-20.32. That's a significant turnaround that really shows why Nadal's head-to-head stat really isn't good enough to make him the GOAT.

Both Djokovic and Federer have reached more grand slam semifinals in their career than Nadal has. The other two are reaching that portion of slams over and over with consistency, while Nadal only gets there when he is in form, giving him a major advantage when they actually do meet. 

The Spaniard has never played Federer at the US Open and has dodged each of the other three at Wimbledon during his struggles on grass over the last three years. If he had to play them even when he wasn't at his best, the head-to-head records would change even more than they did just analyzing the Djokovic-Nadal head-to-head.

So the next time someone claims that Nadal is the GOAT based on his head-to-head record against Federer, Djokovic, and Murray, this is how you can break apart their argument.

Here's a more impressive stat: Total meetings against other three members of the Big Four
Djokovic 109
Nadal 98
Federer 95
Murray 70

Djokovic has met the Big Four more than any of the other members, which is a direct result of reaching the latter stages of tournaments with far more consistency than his three peers. In fact, when you break it down by percentage of total matches played, it becomes even more lopsided.
Djokovic 13.9%
Nadal 10.7%
Murray 10.4%
Federer 7.55%

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