Left, right, left, right…

A couple of weeks ago Ben Torvaney wrote an interesting piece about left footed players converting chances at high rates from the right side of the pitch.

Ben put forward a number of possible theories as to why this might be the case.

I’m going to suggest another one using Steve Fenn’s jazzy viz of my goal keeping data. The data is from the Premier League (nearly 6 seasons worth) rather than the Bundesliga data Ben used, but I think it’s still relevant to the discussion.

In the Premier League overall save % from these wide sections of the pitch on both sides is about 82%. However, as you’ll see from the screenshots, goalkeepers seem a lot more aggressive with their positioning for saves when facing shots from the right side of the pitch (or left as they themselves look at it).

Yes folks, I’m back in comfort zone (CZ) territory again. I’ve shaded the CZ here, so anything outside that I’m considering aggressive. Just 40% of saves are made in the CZ from shots on the right side of the pitch compared to 55% from shots on the left side of the pitch:

New CZ shaded left right viz

These wider, more aggressive attempted save positions not only expose more of the goal, they also reduce reaction time as they’re closer to the shooter.

Also, left footed shots from the right hand side of the pitch (as the shooter looks at it) are more likely to start to move away from the keeper before curving back towards goal than a shot with the right foot. I think this may be a thing.

The graph also shows a slight trend for more goals being conceded at the far side of the goal on the side where keepers are more aggressive:

Where goals go into the netWhy do goalies keep so lopsidedly? It seems there’s a bit of a trend for right handed goalkeepers to be more aggressive in their positioning when facing shots from their left, and left handed keepers to be more aggressive in their positioning when facing shots from their right. As the majority of keepers in leagues are right handed, it might be causing the skew Ben talks about.

Colin Trainor’s piece about keepers over-protecting their near posts inspired much of my later research into keeping data. Give it a read.

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A great time to enter the managerial market

The Merseyside Derby appears to have fully turned the tide against Everton manager Roberto Martinez and once more we ponder possible candidates for the role.

Lets use 6 seasons of Premier League expected goals data and Tableau!

For a look at managerial style we can plot defensive efficiency (expected goals against/actual goals against) on one axis and attacking efficiency (actual goals for/expected goals for) on the other.

We can colour up each manager by his expected goal difference per game and check the sample size by, erm, sizing each manager up by the number of games managed in the Premier League.

Here’s how it looks:

Manager Style Efficiency with xGD p90If you’re looking at recruiting from those with Premier League experience there’s probably never been a better time. Pellegrini, Benitez, Mourinho and former manager Moyes are all likely available on the market. They all show up extremely well here.

Having tools like these to hand should be standard in Premier League boardrooms. Never should clubs be unprepared in these situations. The information isn;t restricted to the Premier League either. You could have your finger on the pulse of all major leagues. It’s a great way to help inform important decisions.

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