A deeper look at shot locations: we still need Game State

Sometimes, what we intuitively have known for a long time, makes sense in the numbers too. That’s probably a good sign and it is certainly true for shot location. Basically, the further away from goal and the further out of the midline, the worse a shot is. But what about that other new concept, Game State? Can we safely leave that out now that we’ve got shot location? It seems not…

 

Four zones

Yesterday, we’ve seen that we can reasonably split a football pitch into four zones, conveniently named Zone 1 to 4, with each higher numbered zone cutting the conversion chances about a third. For clarity, here’s the diagram of the zones again.

Pitch zones

Shots from Zone 1 are rare (< 1%), but they do deserve their own category because of their extremely high conversion rate (>80%). I will leave Zone 1 out of the next table, since the low numbers only make things messy without adding value.

 

Conversion

The next table focuses on conversion rates at different Game States in Zones 2 to 4. Note that Game States represents score differential, but Game States -2 and +2 contain all teams chasing or leading two or more goals.

Overall conversion GS -2 GS -1 GS 0 GS +1 GS +2
Zone 2

0.222

0.212

0.194

0.211

0.251

0.268

Zone 3

0.082

0.056

0.076

0.072

0.118

0.087

Zone 4

0.034

0.016

0.030

0.033

0.030

0.074

As we already know, overall conversion drops sharply as we move up the Zones. However, the most interesting finding is that conversion within a zone is strongly linked to Game State. This means that using shot location is important, but independently, one should also factor in Game State. So, high quality shots are even more high quality if a team is leading a match.

Obviously, shot quality is not directly influenced by the score board, but we consider it a proxy for defensive positioning. As teams chase a goal, they give up defensive effort to gain more offense. Subsequently, as we now find out, their opponents can generate higher quality shots, independent of location.

 

Leading and chasing

So leading teams fire in better shots, but do Game States also influence the amount of shots that teams take from different zones? Do leading teams fire in more close range shots?

To answer that question, we need to study shots, zones and Game States in a slightly different way. The next table shows the relative amount of shots that teams take from Zones 2 to 4 given their particular Game State. Remember, Zone 1 is left out, so numbers in the columns don’t exactly add up to 100%.

Shots

GS -2

GS -1

GS 0

GS +1

GS +2

Zone 2

0.357

0.360

0.354

0.348

0.360

0.387

Zone 3

0.277

0.270

0.267

0.265

0.296

0.312

Zone 4

0.358

0.361

0.371

0.379

0.335

0.293

Overall, teams take most shots either from Zone 2, which is mainly the central penalty box area, where conversion lies around 22%, or from Zone 4, which is the near hopeless area of 3.4% conversion. But Game States do influence where teams take their shots from.

As expected, teams that defend a lead, either by one goal or by two goals or more, decrease the frequency of low quality shots (Zone 4) to below 30%. Also, leading teams have the highest proportion of high quality shots (Zone 2, > 38%).

Interestingly, the highest proportion of low quality shots (Zone 4) is not fired in by teams chasing a lead, but at an even Game State. This links in well with the earlier observation that conversion rates dip significantly at this Game State. It is true, however, that teams chasing a single goal (GS -1) also fire in a high amount of low quality shots (Zone 4, > 37%).

Conclusion

If we link these two tables together, we can learn that leading teams take more shots from good positions (Zone 2) and less from hopeless positions (Zone 4), but their conversion rate from each zone is also significantly higher. So, it works two ways when teams chase leads: they sacrifice defense by giving up more Zone 2 shots that also stand a higher chance of finding the net.