Converting Shots – Repeats and Repeatability 1

So there’s been lots of recent ‘chat’ on Twitter about how much conversion rates vary and how much of it is down to skill or luck. Well, we’ve got some data here at Differentgame so we thought we’d wade into the debate with some of it.

We say ‘wade’, we’re not skilled mathematicians here at all, so it’s actually just dipping our toes into the water with arm bands on and floats at the ready.

Spurred on by this piece on penalties by @JamesWGrayson and encouraged by @simongleave we’ve slowly fumbled our way around creating a couple of funnel plots. If it’s all wrong blame Google. We always feel painfully inadequate reading the tagline for James’ blog: ‘Maths a seven year old is capable of’. Maybe this is a seven year old whose parents are putting him through his 10,000 hour paces…

Ok, enough of the waffle. For this first post (we’ll be doing the other areas soon) we concentrated on shots from the central area inside the box. This is the most dangerous attacking area where it’s easiest to convert chances. The data covers each of the 60 teams contesting the Premier League over the last 3 seasons:

The straight black line through the middle represents the league average conversion rate over the last 3 seasons. We see the ability of Manchester United to be consistently well above average here. We can see how good Chelsea have also been here, being able to consistently beat the average comfortably in this time.

At the bottom of the chart we see how dismal Wigan have been in 2 of the last 3 seasons in their conversion. West Ham too. However, under Sam Allardyce, the Hammers have been able to manufacture well over 50 more shots from these good areas than they did in 2011 under Avram Grant. That’s despite taking nearly 100 shots less overall too.

The second graphic shows the situation for most of the top strikers over the last 3 seasons:

The black line through the middle here represents the average conversion rate of the strikers in this sample. It’s 7% above the average for the league, but then they’re mostly playing for the best teams.

Here we see the same names being on or above average in this elite band. Berbatov’s name appears three times despite joining Fulham for season 3 (although this is where his conversion is worst). Chicharito’s name appears three times too. Robin van Persie is there twice – once for Arsenal and again for this year’s United performance. Despite everyone being unhappy with Rooney’s seemingly deteriorating performances his conversion has actually been better over the last two years.

We especially like Bale and Walcott’s plots here. Despite their wider starting positions on the pitch, they’re as good as the elite with their conversion in the central areas of the box.

We’d really like some comment from those with a better knowledge of interpreting these things about the spreads on show here, so get Tweeting, even if it’s to point out where we’ve gone wrong.

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