Attacking Efficiency: Conversion Rates a Deep Dive

As we look to examine how effective our teams are we try to ensure we don’t waste our chances. We work hard to win and maintain possession and for this work we want our play rewarded with scores. The challenge is that there are multiple ways of assessing how efficient our attacking play is. In a series of posts, I’m going to look at how we can conduct an in-depth analysis of how effective our attacking play is.

To begin this series I’m going to take a look at how we examine one of the key aspects of our attacking play; Shooting. We will examine various methods of calculating conversion rates. A conversion rate is essentially the percentage of shots that result in scores. This helps us measure how efficient we are in taking our chances in a game. However, minor adjustments to the calculation as you will see below will change the rates.

General Total Conversion

A basic conversion rate is a simple metric to see how efficiently we shot the ball. It is calculated by dividing the number of scores by the number of attempts on goal. This tells us what percentage of our chances we are converting into scores. Over time we can identify season trends around how our attacking is contributing to our results. This metric is a good start to give you an overview but is limited. For example, it treats goals as only one score but doesn't take into account how they are worth 3 compared to the point that a goal is worth. Your overall conversion rate could also be distorted perhaps by a highly effective free-taker and it may mask issues you have when it comes to shooting from play. To show this in practice

Dividing conversion rates from play and from Set Pieces.

To avoid your conversion rate being distorted by being significantly better or worse from set-pieces calculate the two conversion rates separately. This will give you a focused look at your free-taker and your forwards from play. This insightful way of looking at conversion rates will allow you to identify whether you are more effective from dead balls or from play. In the age of the offensive mark as a set piece this breakdown could help you examine your forward in more detail an inform your game plan for creating chances. If you felt like you wanted to separate the set pieces from the mark and calculate 3 different conversion rates then would also provide an even more detailed breakdown of your attempts on goal.

Effective Conversion Rate

Effective conversion rate is a slightly more complex way of calculating a conversion rate. It adjusts the conversion rate to take into account the fact that a goal is worth 3. It is similar to EFG% (Effective Field Goal percentage) used in basketball that takes into account the different value of shots. It rewards players and teams accordingly for converting goal chances.

It is calculated using the formula (PS + 3*GS)/ST

Where PS = Point Scoured

Where GS = Goal Scored

Where ST = Shots Taken

By taking into account the value of different scores our effective conversion rate is more reflective of how effective we were with our chances. The risk of using this metric is that it will hide forwards and attacking units who may waste chances multiple simple point opportunities but have these misses masked by a goal which will drag up the effective conversion rate. In addition to this, it doesn't punish the team for passing up goal chances in the same proportion as it rewards them for making them. By not considering the value of chances missed it may mask some of the team's actual flaws.

The reality is that all of the variants of a conversion rate offer some insight into a team's performance. They measure our shooting efficiency in different ways but inform coaches and players whether they are taking their chances from different perspectives. They can be biased and if used in isolation could mislead you so it is important like any KPI to consider them in the context of a full game and a full season.

If you found this useful stay tuned for the second edition of this blog post where we discuss attacking efficiency, creativity and productivity as measures to assess your attacking play.