Blog of Random Thoughts and Pictures

Expected Goals (xG)

May 9th, 2021

As part of my LOI weekly predictions (don’t ask about match day 10 it was a wipe out) I’ve also included an indication of the teams expected goals (xG). Now it might be worth articulating an introduction to expected goals and there are four videos worth a review.

  • One by David Sumpter (Friends of Tracking)
  • One by Duncan Alexander at Opta.
  • One by Tifo football.
  • One with example goals with the xG overlaid on the screen.

First up David Sumpter on How to explain expected goals to a football player.

In this video David takes us through the probability of scoring a goal in the penalty area, with an overview of Barcelona statistics of expected Goals, indicating how a penalty is a 75% chance of scoring, and in comparison to a 7% chance of scoring, and an explanation of what this means.

True to the point there can and should be a reasoned discussion around goal scoring (and goal prevention) instead of always the emotional one, and xG gives some insights on this.

Opta’s Duncan Alexander takes us through the expected goals metric in the video Opta Expected Goals.

Of note (agt the time of the video), 4 variables are considered with Opta, Assist Type, Header / Foot, Big Chance and Angle/Distance.

The video by Tifo Football is a nice By The Numbers presentation on What is xG ?

They describe in nicer detail how good a shooting chance was, how likely a similar chances was, to result in a goal. They also highlight that people like StrataBet considers defenders in the way while other models like Opta do not and that sets of 5~10 games get best value for xG.

Expected goals (xG)

So expected goals (xG) is a probability of scoring a goal, with a look at how good a shooting chance was, how likely a similar chances was, to result in a goal.

Finally here’s a video demonstration of expected goals (xG)

LOI Matchday 10 Predictions

May 6th, 2021

First up news of the week in LOI has to be the dismissal of Kevin Sheedy from Waterford FC. I think the writing was on the wall from early on, dare I say before the season even started. Back to the drawing board for Waterford. Before making a prediction on their game, and the four others for matchday 10, a review of match day 9 shows a 3 out of 5 result, with two draws called correctly.

The running total is 20 correct results out of 45.

Now to the predictions for matchday 10

Derry City (64%) vs Longford (14%)
The Probability of a Draw between Derry City and Longford is 20%

The number of sim home wins for Derry City is = 8
The number of sim away wins for Longford is = 1
The number of sim draw is = 1

Derry City (1.0xG) vs Longford (0.78xG)

I went for a Derry win last week and it didn’t work out, but the predictions are aiming towards a Derry win again here, and so we stay with the Derry win (predicted)

Dundalk (61%) vs Sligo Rovers (16%)
The Probability of a Draw between Dundalk and Sligo Rovers is 22%

The number of sim home wins for Dundalk is = 5
The number of sim away wins for Sligo Rovers is = 2
The number of sim draw is = 3

Dundalk (1.41xG) vs Sligo Rovers (1.42xG)

Sligo are scoring away from home (xG) and these two teams had a draw on the opening day of the season. Data says Dundalk win, the heart says draw, but will go for the Dundalk win.

Waterford (55%) vs Drogheda (21%)
The Probability of a Draw between Waterford and Drogheda is 23%

The number of sim home wins for Waterford is = 6
The number of sim away wins for Drogheda is = 2
The number of sim draw is = 2

Waterford (0.62xG) vs Drogheda (0.76xG)

This will be a tight game again, well mainly a 0-0 type match, but the data is pointing towards a Waterford FC win, and we all need some cheering up, so a Waterford win in this one.

Bohemians (58%) vs Finn Harps (16%)
The Probability of a Draw between Bohemians and Finn Harps is 26%

The number of sim home wins for Bohemians is = 3
The number of sim away wins for Finn Harps is = 3
The number of sim draw is = 4

Bohemians (1.38xG) vs Finn Harps (1.26xG)

I’m going to call a draw in this one, the simmed matches and xG are indicating a draw and Finn Harps are tipping along nicely and I cannot push for the Bohs win, so a draw it will be.

St. Patricks (33%) vs Shamrock Rovers (38%)
The Probability of a Draw between St. Patricks and Shamrock Rovers is 29%

The number of sim home wins for St. Patricks is = 2
The number of sim away wins for Shamrock Rovers is = 4
The number of sim draw is = 4

St. Patricks (1.59xG) vs Shamrock Rovers (1.23xG)

And finally to the top of the table clash and this has a draw written all over it, and so another draw.

LOI Matchday 9 Predictions

May 2nd, 2021

It’s getting harder to keep up with all the matches happening in the LOI, but at least match day 8 (in review) was a good one as another 4 predictions out of 5 were on the button. Although I was way off the the one that was incorrect with Bohs getting beaten by Derry City, could anyone have seen that coming ?

The running total is 17 out of 40.

Now in to match day 9 predictions.

Drogheda (32%) vs Bohemians (41%)
The Probability of a Draw between Drogheda and Bohemians is 27%

The number of sim home wins for Drogheda is = 2
The number of sim away wins for Bohemians is = 6
The number of sim draw is = 2

Drogheda (1.12xG) vs Bohemians (1.45xG)

This is too close to call and so going for a draw.

Shamrock Rovers (58%) vs Waterford (18%)
The Probability of a Draw between Shamrock Rovers and Waterford is 24%

The number of sim home wins for Shamrock Rovers is = 3
The number of sim away wins for Waterford is = 6
The number of sim draw is = 1

Shamrock Rovers (2.09xG) vs Waterford (0.62xG)

The sim matches are playing tricks with me, but the call here has to be a Shamrock Rovers win

Longford (11%) vs Dundalk (69%)
The Probability of a Draw between Longford and Dundalk is 17%

The number of sim home wins for Longford is = 2
The number of sim away wins for Dundalk is = 7
The number of sim draw is = 1

Longford (0.77xG) vs Dundalk (1.2xG)

Dundalk are on a roll now and I’ll take them for a win in this one.

Sligo Rovers (36%) vs St. Patricks (35%)
The Probability of a Draw between Sligo Rovers and St. Patricks is 29%

The number of sim home wins for Sligo Rovers is = 4
The number of sim away wins for St. Patricks is = 4
The number of sim draw is = 2

Sligo Rovers (0.89xG) vs St. Patricks (0.90xG)

This is looking like a draw and will call it for a draw.

Derry City (61%) vs Finn Harps (15%)
The Probability of a Draw between Derry City and Finn Harps is 23%

The number of sim home wins for Derry City is = 6
The number of sim away wins for Finn Harps is = 2
The number of sim draw is = 2

Derry City (0.83xG) vs Finn Harps (1.08xG)

I wonder is Finn Harps early season bubble about to burst with Derry catching them ? All the pointers are towards a Derry City win so will go for a Derry win.