Welsh Hiraeth verses English Passion.

No sport likes to invoke the seemingly unquantifiable measure of heart, passion or sheer will to "want it more" than the opposition than rugby union.

Whether it be the sight of grown locks crying at the first strains of "Mae hen wlad fy nhadau" or the emotive interplay between team and crowd in "Flower of Scotland", the importance of beginning and staying in a positive mental state is a constant aim.

It is perceived that the more concentrated the mental state of the players and team as a whole, the more positive the results achieved and following Wales' brave, but ultimately slightly disappointing comeback in drawing 16-16 after taking a late lead in Ireland, coach, Warren Gatland has demanded the side "be better emotionally".

Dr Roberts & Captain Sam gear up for pre Six Nations singing practice.

Already there's a sneaking suspicion among those more comfortable with statistical rather than emotional indicators that such demands are the product of already knowing the actual result rather than any readily identifiable stage in last week's match when Welsh passion waned and Irish fire rekindled.

Measuring emotional levels among the players will require much more sophisticated monitoring than the current gps and a trained, if biased seasoned eye.

However, the single rugby event when amateur psychologists and stats followers get to stare into the soul or the kicking percentages of the player is during a kick to the posts.

The slightly robotic routines of a Wilkinson or a Farrell has evolved into the free form improvisation of the "Biggarena", but the aims of all are the same. To put the kicker into a state, both emotionally and physically to give himself the best chance of converting the kick.

Although a kick is a kick they arise through two distinct events. Either they are a conversion of a try or a penalty kick as the result of foul play.

Currently the rewards in international and major club rugby gives the side an additional two points to the five already won from the try in the case of a conversion and a stand alone three points for a penalty kick from an opponent's transgression.

So already there is a perhaps major disconnect between pressurized situation of a penalty or a conversion.

In the case of the latter, hard earned points are already on the board because of the try and numerically the value of the kick is just two rather than the three points on offer for a penalty.

Additionally, in the case of the penalty, the side has yet to add to the scoreboard despite playing well enough within the previous open play phases to force the opposition into a major infringement.

Simplistically the pressure may be conceived as being greater on the kicker when taking a penalty rather than when he is merely adding the "extras" from a conversion. Even with a choreographed comfort blanket, his actual level of performance may be lower in the higher stress levels of a penalty kick.

Using OptaPro data for kicks of both types, incorporating other variables such as kick distance, angle and pitch location, we can in addition add a variable to account for the type of kick to see if there is a statistically significant difference in success rate that is dependent upon the nature of the kick.

The data runs into five figures, ranging from club, under 20 and full international kickers. In the initial run through a conversion is converted, statistically significantly less often than a penalty once the position and angle of the attempt is accounted for.

So even though a penalty kick is more valuable than a conversion and represents the only chance in that phase of play to add to the score and therefore you would assume places more pressure on the kicker, it is these higher pressure kicks that are successful more often, even when location is accounted for.

Time for the sports psychologists to step in if this analysis persists after this initial data dump. Does a kicker involuntarily relax into a lower performance level when he's trying to simply add points to an already advanced scoreboard?

Maybe Gatland was correct in principle and in the case of kickers particularly. They may need a Biggarena mark 2 to get deeper into the required zone following a George North try, a mass eruption of celebratory Welsh Hiraeth and the comfort zone of knowing points are already in the bag as a reward for a period of dominant play.

Welsh proof read by Rachel Taylor and Dr Ian Graham!

The Shawcross Redemption.

Stoke fans are restless again.

A couple of weeks after eagerly anticipating a Wembley trip and making a push for a domestic cup double, settling for 4th place in the Premier League and regular trips to the Nou Camp, while fighting off the advances of Chelsea and Manchester United for the services of Mark Hughes, they've seen all this fade to grey.

They're now wondering how Hughes could be so inept as to neglect Stoke's defensive and attacking frailties in the January window and when he should go to avoid regular trips to the Pirelli Stadium, Burton.

Knee jerk punditry has nothing on those with an emotional and financial investment.

Top of Hughes' current rap sheet in the eyes of his previously greatest supporters is his neglect of adequate cover for the central defence.

It probably doesn't help that on the same weekend that Robert Huth (allowed to leave on a free) was visibly winning the title for Leicester, Stoke captain Ryan Shawcross was again sitting out a tame home defeat to Everton through another injury.

With Huth & Shawcross in tandem, Stoke often dispensed with the services of a keeper.

With or without stats are horribly blunt devices, where small win/loss samples can "prove" bit players essential to a side's well being, when they are merely the coincidence with little causation.

But just as action or heat maps for a single match for more numerous in game stats may shed some light on where a side won or lost a single game, aggregating such things as the quantity and quality of chances allowed with or without a particular player may also tell us something about their impact.

Shawcross has obligingly missed about half the season through injury and the odd suspension. Here's the expected goals per 90 that Stoke have allowed when he's played and when he hasn't in the Premier League. (excuse the familiarity in the table, it was done for a Stoke fan site).

So there is tentative evidence that a player who has had his fair share of media scrutiny has become an important, if not irreplaceable part of Stoke's defence.

His most obvious attribute is his strength in the air and his ability to prevent attackers winning the aerial challenges (often, and in keeping with many defenders, by anchoring the attacker to the ground by his shirt tails).

If you look at the number and proportion of headed chances conceded when Shawcross is and isn't on the field again the contrast is marked. 20% of the total attempts come from headers in his absence of which five have resulted in goals compared to nearer 10% when he plays, with no goals conceded.

It has been suggested that the skill differential when players use their head is greater between players than when they use their best foot, so for once the fans may actually have a point when they debate that Stoke have one of the Premier League's best defensive headers of the ball, but nothing in the way of cover.

Putting Your Best Foot Forward.

Finishing skill has been an acknowledged fact of football virtually forever. Strikers are never more dangerous than when they are being "clinical", "ruthless" or, for those of a certain comic strip vintage, "Dead-Shot".

Unfortunately this almost mystical ability has constantly eluded every effort to pin it down even as the data generally available becomes more extensive and plentiful.

It is relatively easy to find strikers who are under or over performing their expected goals model based on any number of shot location variables, but persistence of this trait is less obvious.

Often the "cold" player from one month/week/match/half is the same "hot" scorer from a similarly recent time frame.

   The Magical Finishing Skill Aura of "Dead Shot" Keen's boots worked for Billy Dane. 

Shot volume and location can usually be relied upon to produce an expected goals figure that tracks fairly well a player's actual goal tally. But expecting even a season-long over performance to extend to a subsequent season (at least with a rudimentary model) is often a forlorn hope.

Random variation or rare or unlogged events, such as deflections and defensive pressure appears to overwhelm any attempt to observe a quality that is currently worth around 2 billion Chinese yuan.

A player may differ in finding space, receiving passes and anticipating where to be inside the box, but it is likely that the difference in finishing ability once the chance presents itself is going to be small between the elite.

Marginal gains, but also expensive mistakes if luck is purchased masquerading as a repeatable talent.

The biggest talent gap in finishing skill at the top level should lie between strikers and the rest of the outfielders.

So I looked at every shot (headers excluded) taken by every oufield player in a chance created solely from open play, which wasn't deflected and created an expected goals model based simply on the location of the shot. Sample size well into five figures.

Unsurprisingly, the location of the attempt in this sanitized shooting competition was a significant indicator as to the likelihood of a goal being scored.

I then told the model which shots were taken by "Dead-Shot" strikers and which came from the boot of non-strikers. The expectation being that this additional variable would prove significant and improve the likelihood of the strikers scoring at the expense of their team mates who were less talented at finishing (or they would presumably be strikers themselves).

It didn't.

In this dataset, knowing that a striker had taken the shot slightly decreased the likelihood of a goal, but this effect had almost certainly arisen entirely by chance. The model couldn't see a difference in the likely outcome regardless of whether the shot came from a defender or a striker.

If there is a difference in finishing ability between Premier League outfield players in different positions, as opposed to other desirable attributes possessed by a striker, a naive shot location model can't cut through the missing variables and noise to find it.

So instead I looked for a set of Premier League shots that should/might be (much?) less likely to be scored than others and could be picked up by a simple shot location model.

Scorcher's Billy Dane aside, most players don't have magical football boots, but they do have a preference for one foot over the other. I've yet to find a penalty taker who hasn't taken all his kicks exclusively with a particular foot.

Regular penalty takers used their penalty taking foot for nearly 80% of their shots from opportunities created in open play. So you also have to think they know something about the "finishing ability" of their standing leg.

I re did the model.

Again in the model shot location was a significant variable in the outcome of the shot. But this time when I added a variable for whether the shot originated from the player's penalty or non-penalty taking foot, that too was (almost) significant.

Benchmark figure, a shot with a player's "weaker" foot reduces the chances of a goal by around 10% of the value if it had if it had been taken with his penalty kick foot.

Every player demonstrates finishing ability and that difference might show itself on the 20% of occasions he uses his "swinger" and hits and hopes.