Stoke Statistically since 2016/17

[tachyon]

I've taken a look at our underlying stats since the start of the 2016/17 season.

Premier League teams increasingly evaluate themselves in terms of "expected goals". They rate the quality and the quantity of chances they create, rather than the actual number of goals they score and allow.

The stat has been featured after games on Match of the Day this season.

It tells you if a team has a sound process, rather than relying on just actual goals that are often streaky in nature and prone to randomness or "luck".

If you have a good process, eventually you will tend to get the rewards you deserve, and if you have a poor process, the same is unfortunately true.

Stoke's process has trended from that of an average mid table team at the halfway stage of the 2016/17 season to that of a relegation side, currently.

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Here's our plot from the start of 2016/17 to now.

The orange line shows the amount and quality of chances we are allowing our opponents per game.

It was around 1 expected goal per game at the start of 2016/17, slightly better than average and it is around 1.7 expected goals now. One of the worst in the league and continuing to climb.

Chance creation isn't as seriously troubled as our defensive metrics, but that too has declined from 1.2 at the start of 2016/17 (broadly average for the league) to around 1.1 expected goals per game, now.

If you look at the expected goals of all 20 sides and their current points/ goal difference totals and simualte the remainder of the season, Stoke go down in around 30 percent of these simulations.

So we're in trouble, but not beyond being saved. particularly by a more solid defensive process.

[Deleted]

The expetcted goals against trend is awful. How could the club not have spotted this? It was clear to the naked eye we were giving up huge chances every game.

Biggest jump seems to coincide with us going to 3 at the back.

[tachyon]

It's difficult not to draw that conclusion. Basic in house statistical analysis should have picked it up, but as you say, it was probably clear from the simple eye test. The xG trend is one of the worst I've seen for years, unfortunately.

[tachyon]

Here's Man City's xG trends. Frightening, even with their financial clout.

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[Deleted]

Wow

Out of interest, if you have the data, what was QSF xG like at Espanyol compared to his predecessor ?

You like us to take a chance on potter?

[tachyon]

Espanyol overall have been fairly solid defensively, both under QSF and his predecessors.

You always get blips in LaLiga depending upon when you get served up Barca & R Madrid as opponents. So the big blip is just the big two's xG running through the system.

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[tachyon]

Potter's a risk coming from a relatively low profile league, where innovative tactics tend to work well. Ostersunds use analytics and their league positions have been under pinned by solid fundamental stats (xG etc), but it is easier to get a competitive advantage in weaker leagues. His Europa run will have raised his profile & I suspect he'll have clubs queuing up for his services, but pitching into a relegation battle with only half a season to go, doesn't immediately scream "good deal" for either Potter or us.

[Northy]

So, basically it's gone to shit since we signed Berahino ....

[tony1234]

"I don't see what everyone is worrying about"..... well in that case, you have absolutely no handle whatsoever on your business and a lay-person knows more about your problems than you do

[mermaidsal]

Fascinating - and no surprise to see the maths say what we've most of us been saying here since the rot set in, down almost to the week it started.

[Deleted]

Expected goals? I expect em to miss nearly every time! Sad but true!

[Pricey]

Best post I've ever seen on here. Nice work.

[tachyon]

Here's another problem we have.

It's not a dig at the particular player because keepers are inevitably under the spotlight and due to the partly random nature of scoring events, their success in saving attempts can vary considerably.

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This plots Jack Butland's rolling average save rate compared to his expected save rate.

You first model how likely a shot is to go in based on shot location, shot type, power, placement, whether it was deflected etc and then you compare these numbers to how many goals the keeper actually concedes.

Jack's not having a great season.

If a keeper is saving more than you'd expect based on the quality of the chances his defence is allowing, you'll see the blue actual line below the orange expected line. That's obviously what you'd want.

Unfortunately, the opposite has been true for large parts of this season, although Jack's numbers have improved of late.

We're hopefully just emerging from a defensive perfect storm.

[tachyon]

One more chart.

This is used as a quick health check to see where there's room for the team to improve.

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It's colour coded.

Blue is above average, the darker the better.

Red is below average, the darker the worse it is.

First column is the average expected conversion rate based on the quality of chances a side is creating. Chances in the six yards box are higher quality than long range shots from 30 yards.

League average is 10% and we're league average.

That column's paired with the third column, the number of chances we've created this season. We're below average here.

Second column is the average conversion rate of chances we're allowing, again based on their quality.

12.3$ is the worst in the league, tied with Liverpool!. They get away with it because of their attack and they've only allowed 168 attempts on goal to our 307 (fourth column).

In summary all red is BAD, mostly blue is GOOD.

footnote.

Burnley allow lots and lots of low quality chances......that was us under peak Pulis.

Read more: oatcakefanzine.proboards.com/thread/275712/stoke-statistically-2016-17?page=1&scrollTo=5876009#ixzz549bFXrJc

[StoKeith]

Jan 13, 2018 13:39:42 GMT tachyon said:

Espanyol overall have been fairly solid defensively, both under QSF and his predecessors.

You always get blips in LaLiga depending upon when you get served up Barca & R Madrid as opponents. So the big blip is just the big two's xG running through the system.

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Nice graphs.

You should take a rolling 5 match average to smooth out the blips caused by teams like Man City and Barcelona.

Either way, it doesn't look good for us.

[tachyon]

They're rolling 6 game averages, it's just that Barca are that much better than most of La Liga.