The Effect of Variance? Part One - Improvers in 2016


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April 1st, 2016.

One notable market phenomenon is the over compensation for recent results, or 'form'.  This is very often a mistake, with Tennis being a sport dictated by fine margins.  

There have been many, many occasions where a Futures or low ranked Challenger player has qualified or received a wild card to an ATP event and somehow got to the quarter final, or beat a relatively accomplished player in the first round before losing in the second round.  Following this, the market then prices them up like a strong Challenger player in their next Challenger event, thinking that somehow this player has turned the corner.  It's the same in the WTA.  Women are notoriously streaky players with very inconsistent levels, frequently capable of beating player x one week and then getting demolished by the same opponent soon after.  

Of course, there are some instances where a player achieves strong results compared to their ranking and there will be a reason behind that.  Perhaps they are a young prospect on an upward ability curve, or they are returning to tour from their injury, or their stats in Challengers/Futures will be much better than their rank suggests.  

On that basis, what I thought I'd do for this article is look at the ranking risers and fallers in the ATP so far in 2016 and see if these ability changes were reasonable based on stats and logic - effectively whether the player's rises and falls are justified.  

To commence the research, I took the player's rank at 4/1/16 (the start of the 2016) season and compared it to their rank on 31/3/16 (today), and applied a 0.7 (improving)/1.3 (declining) multiplier to see if their ranking was within those boundaries.  For example, Jo-Wilfried Tsonga's rank of 10 had boundaries of 7 (improving) and 13 (declining).  

The following players were shown to have improved their ranking by a ratio of 0.7 or below in the first three months of the 2016 season:-

Guido Pella 74->39 (0.53)
Sam Querrey 59->34 (0.58)
Nicolas Mahut 71->42 (0.59)
Pablo Cuevas 40->25 (0.63)
Martin Klizan 43->27 (0.63)
Alexander Zverev 83->52 (0.63)
Andrey Kuznetsov 79->51 (0.65)
Paul-Henri Mathieu 95->62 (0.65)
Gael Monfils 24->16 (0.67)
Rajeev Ram 89->61 (0.69)
Dominic Thiem 20->14 (0.70)

It's clear that all of these eleven players have enjoyed strong ranking rises in 2016, but which of these players are benefiting from positive variance (luck) and which players are improving because they are simply getting better?

Guido Pella (Age 25):-

25 years of age is quite old for a player to have a breakthrough season, so analysis of the reasons for Pella's success is critical.  The Argentine was in good form in clay challengers in 2015, claiming four titles and losing in the final of Heilbronn to fellow improver Alexander Zverev.  

However, this isn't necessarily a good enough reason for a player to somehow vault into the top 40 of the world, but his hold/break stats from his 13 matches at ATP level this year indicate that he has improved significantly, holding 80.8% of service games and breaking opponents 21.1% (combined 101.9%).  This combined figure would be very similar to expectation for a player of his rank.

Having said this, there is one big problem for Pella.  He's currently saved 5.3% more break points than service points won (ATP average is 2.1% FEWER), so he's running at 7.4% more breaks point saved than the ATP mean.  Similarly on return, he's converted 7.7% more break points than return points won (ATP average is 2.1% more) so he's running at 5.6% more break points converted than the ATP mean.

In total, he's 13.0% up on expectation on break points in 2016 so far, and this is absolutely unsustainable.  His hold/break stats are good because he's been incredible at break points.  I've analysed break point data a lot and I've never seen any player sustain these rates of saving/conversion long-term.  I'll go as far as to say it's absolutely impossible.


However, based on my poll, the world of Twitter has been completely taken in with Pella's 'improvement', illustrating how the market reacts far too much on results and not enough on the reasons behind those results.

VERDICT: UNSUSTAINABLE IMPROVEMENT

Sam Querrey (Age 28):-

Three years older than Pella, Querrey has had a volatile ranking, fluctuating from a career high 17 to just shy of the top 100 within the last five years, and this is quite symptomatic of market perceptions of the American.  

Excellent results in his home country are negated by horrific results abroad, and looking at his three year data across all surfaces, Querrey has held serve 85.5% and broken opponents 15.8% (combined 101.3%), indicating that his current ranking of 34 isn't far from where it should be.

Interestingly, those three year stats also show that Querrey has underperformed by 1.9% against his expectation for saving break points on serve, and by 0.8% converting on return, showing that he could actually be better even if he was just average at key points.  

In 2016, he's over performed across both metrics overall by 1.0% in his 18 matches on tour, so his strong results are a slight over-correction in variance.

VERDICT: CURRENT RANK NOW CORRECT, VARIANCE/POOR KEY POINT MENTALITY AFFECTED CAREER

Nicolas Mahut (Age 34):-

Coming towards the end of his career, Mahut is enjoying something of a renaissance although with eight wins from 15 matches this year he has over performed his combined hold/break percentage of 98.2% (I'd expect his record to be around 6-9 instead of 8-7 with this percentage).  

This is simply down to him over performing on key points on return, converting 44.4% of break point chances but winning just 36.0% of return points (6.3% above expectation). His match against Jeremy Chardy in Rotterdam was a prime example - Chardy was considerably the better player, with seven break points compared to Mahut's four, but Mahut won in straight sets because he converted three of those four break points.

Over the last three years, Mahut has underperformed by 0.3% across serve/return break points so this break point conversion rate is clearly variance, and will be unsustainable.  It's likely Mahut will be slightly over-rated by the market in the near future.

VERDICT: POSITIVE VARIANCE 

Pablo Cuevas (Age 30):-

The Uruguayan clay-courter's rank has improved due to strong showings on his favourite surface, with one quarter-final and two titles on clay already from three events in 2016.  

With a 12 month hold/break percentage on clay of 111.3% compared to 98.0% on hard/indoor hard, it is clear that Cuevas is something of a surface specialist, and his rank will fluctuate based on the surfaces of tournaments.  Those stats also illustrate Cuevas is better than his current rank of 25 on clay, and much worse on other surfaces.

VERDICT: SIMPLY GOOD ON CLAY

Martin Klizan (Age 26):-

Klizan's first ATP 500 title, in Rotterdam (he beat Mahut in the final) propelled his ranking into the top 30 but with a 12 month combined hold/break percentage of 97.1% it's difficult to make a case for him being a top 30 player (more like 50-60).

In Klizan's 14 matches so far this year, he's boosted his combined percentage to 104.8%, mainly because he's performing 5.1% above expectation for saving break points and 3.6% above expectation for converting them (8.7% overall).

Effectively his profile is very similar to Pella - over performance on break points making a big impact into his ranking, although it's worth noting that Klizan over performed on break points by 4.2% over the last three years, so he might actually be very mentally strong at key points to an extent.

VERDICT: POSITIVE VARIANCE ON BREAK POINTS, ALTHOUGH EVIDENCE OF STRONG MENTALITY

Alexander Zverev (Age 19):-

As one of a number of strong young prospects on tour, Zverev's improvement is absolutely logical (although similar prospects Borna Coric and Hyeon Chung's ranking has stagnated of late).  

Running at a combined 100.6% across all surfaces this year, Zverev is arguably better than his current rank although it's worth noting he's also over performed on break points overall by 3.8%.  If he was neutral on break points, his current rank would be about right.

Twitter felt Alexander Zverev has improved significantly this year...

VERDICT: FAIR RANKING WITH LIKELY FURTHER IMPROVEMENT

Andrey Kuznetsov (Age 25):-

I must admit I did not see Kuznetsov's improvement in 2016 coming at all!  

The Russian actually over performed on break points by 5.3% in 2015 despite winning just eight main tour matches all season, yet this year already he is 12-6 in three months, over performing on break points by a lower 3.2%.  

I have literally no statistical explanation for Kuznetsov's rapid improvement.

VERDICT: NO STATISTICAL EXPLANATION

Paul-Henri Mathieu (Age 34):-

As with countryman Mahut, Mathieu has improved his ranking notably this year.  This was despite him over performing by 6.3% across break points on serve and return in 2015, when he only achieved seven victories on the main tour from 19 matches.

However this year he's over performed by an incredible 13.0% on break points, which is completely unsustainable and the absolute reason why his 2016 record is relatively strong at a current 5-5.  

VERDICT: SEVERE OVERPERFORMANCE ON BREAK POINTS - UNSUSTAINABLE

Gael Monfils (Age 29):-

The talented Frenchman has a career high ranking of seven, so being ranked outside the top 20 at the start of the year was almost certainly a rank below his ability, and Monfils did suffer from several injuries last year (as with this year as well).

This has been corrected with a rise this year despite his poor performances saving break points (3.3% below expectation).  With a 112.7% combined hold/break percentage in 2016, (106.3% in 2015, 108.8% in 2014, 106.5% in 2013) it's arguable that Monfils is playing some of the best tennis of his career and it's also reasonable to think that Monfils' ranking improvement will continue.

VERDICT: JUSTIFIABLE IMPROVEMENT BASED ON STATS

Rajeev Ram (Age 32):-

Another veteran to make the list, the American has performed admirably in both singles and doubles in the last year or so, often recording value wins on my model at big prices.  His current rank is actually a career-high.

Ram's 2015 activity was largely consigned to the Challenger Tour (he only played 13 ATP main draw matches last year) but he's already played 16 ATP matches this year, taking advantage of direct entry into tournaments now that his ranking has improved to inside the top 100.

Despite this, Ram has underperformed by 5.5% for converting break points and his success can largely be attributed to a severe over performance in tiebreaks this year (9-2 record).  A record like that will win a player a lot of tight matches.  He's also 15-13 for sets ending 6-4/7-5/7-6 in 2016, despite average Pinnacle starting odds of 3.72.

It is almost impossible to sustain a high tiebreak win percentage unless you are either a top player or John Isner, so I'd expect these stats to correct themselves in the long-term.  

VERDICT: WON A LOT OF TIGHT SETS/MATCHES - UNSUSTAINABLE

Dominic Thiem (Age 22):-

Thiem is just one of two players aged below 25 in this list, and the young Austrian certainly looks to have kicked on to a strong effect this year.  This was also felt by the world of Twitter, despite his 0.7 ranking improvement ratio being the lowest in the list:-

Even though this improvement ratio was lower than the other players in the article, it's arguable that it is more difficult to improve ranking in the upper echelons of the ATP as quickly as the lower ranks, and if the metric 'ranking points gained in 2016' was used instead of % of rank improved, he'd be much closer to the top of the list.

Thiem's 2016 data shows a stark improvement to his stats from 2015.  Last year, he held serve 83.5% and broke opponents 20.0% (103.5%) and underperformed for saving break points by 2.5% and underperformed converting break points by 4.9% (overall 7.4%), so an improvement in those 2015 stats would have been extremely logical unless he was a mental midget at key points.

In 2016, Thiem has held 83.2% and broken 25.4% (combined 108.6%) although has still underperformed on break points by an incredible overall -14.0%.  With this in mind, it is clear that Thiem can still improve to a huge extent and a big career beckons unless this reflects a big mental deficiency.

VERDICT: KEY POINT UNDERPERFORMANCE IN 2015 & 2016 - IF THIS IS VARIANCE HE WILL HAVE A SUPERB CAREER.

CONCLUSION:-

Of the eleven players that fitted into the 0.7 improvement ratio, just two were below 25.  I'd have expected more young players to feature here, although this perhaps indicates that young players generally improve slowly and surely as opposed to making vast strides quickly.

The reason for a number of older players being included in the list is clearly positive variance.  Pella, Mahut, Mathieu and Ram are almost certain to be unable to sustain their key point data and shows that they are better ranked than their current ability, and this can also be argued to some extent for Klizan as well.  

The data in this article clearly indicates that looking at match results is clearly not enough to be able to accurately gauge the level of a player, and deeper research of players and the reason for their 'success' is required for long-term accurate player analysis.
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