Expected goals deliver great expectations – a statistical review of team performance in the LOI Premier Division

As we reach the last few of weeks of the year, now is a good time to reflect on the exciting Premier Division season just gone – it was a League of Ireland campaign that saw Derry City win the league for the first time for 25 years as they shuttled Shamrock Rovers into second place preventing their three-in-a-row.

St. Patrick’s Athletic secured third spot and fourth placed Bohs qualified for Europe only thanks to Candystripes’ FAI Cup win, with Dundalk missing out on Europe all together. Meanwhile UCD return to the First Division after just one season as they finished bottom of the league.

Ok, hold on here you might be saying. Just what is this parallel universe that extratime.com is portraying, one that doesn’t have the Hoops win the league and Harps dropping into the second tier of the League of Ireland?

Well we have been reviewing the season in statistical format, looking at expected goals (xG) for and against and expected points (xPoints) for each of the teams in top flight and, using Wyscout’s information, also seeing what information can be gleaned in terms of formations, ball recovery position, possession and even deep completions.

Your opinion on what is to follow may be somewhat skewed by the fact that the xPoints gave an expected outcome as outlined in our opening paragraphs but we think it worthy of reading on.

Expected League Table

Most people would be aware of the xG models that assign a probability metric to every shot based on historical data from games. The use of big data with xG for and against gives a further metric of xPoints which has been be used to give us an expected league table.

The xPoints show that Shamrock Rovers significantly ‘over-performed’ in the points tally they actually got while Derry City slightly ‘under-performed’ which meant they ‘probably’ should have won the league albeit by the slimmest of margins of 0.7 xPoints.

Rovers’ xG against is the main factor for the xPoints difference between their actual points tally and expected points tally as their xG against was 32 compared with just the 22 goals that Alan Mannus actually conceded – a metric pointing to the importance of the Hoops goalkeeper in wining the title.

The xPoints table gives us the following scenario:

xPosition (Actual)        Club                             xPts (Actual)    Differential

1 (2)                             Derry City                    68.7 (66)         +2.7

2 (1)                             Shamrock Rovers        68.0 (79)         -11.0

3 (4)                             St. Patrick’s Athletic    57.8 (61)         -3.2

4 (6)                             Bohemians                 50.9 (46)         -4.9

5 (3)                             Dundalk                       50.4 (63)         -12.6

6 (5)                             Sligo Rovers                49.4 (52)         -2.6

7 (7)                             Shelbourne                  45.9 (41)         +4.9

8 (8)                             Drogheda United          38.5 (38)         +0.5

9 (10)                           Finn Harps                   38.4     20        +18.4

10 (9)                           UCD                             27.2     26        +1.2                            

Formations

Let’s move away from the prediction models and into reality where we look at what formations teams lined out with across the campaign. Wyscout calculates this based using the players’ position as ‘an average point of all actions where they touched the ball’.

In the ten team top tier, only two clubs didn’t line out in a 4-2-3-1 formation most of the time - Shelbourne (47%) went 5-3-2 while Shamrock Rovers went 3-4-2-1 a third of the time with 3-4-1-2 used a quarter of the time.

Sligo Rovers kept their 4-2-3-1 formation for a higher percentage of the time (74%) than any other club.

Looking at how teams attacked, Derry City went the most down the left (38%) reflecting the importance of Michael Duffy in the latter half of the season and Brandon Kavanagh more in the first half, while Finn Harps went the highest proportion down the right (38%).

Passes and Ball possession

It won’t surprise anyone who followed the league this year that Shamrock Rovers topped the charts for passes (averaging 469 per 90 minutes), pass completion (82% level – same as Derry City) with 59% ball possession. City were second in passes with 444 passes per 90 and ball possession (58%).

This compares with the average figures across the league of 367 passes per 90 minutes and 78% pass completion. The Hoops also had the most touches in the penalty area (19 per 90 minutes) with UCD having the fewest (7).

The Candystripes topped the table on passes to the final third (63 per 90 minutes with 65% accuracy) and through passes (9 per 90 minutes with 37% accuracy) while the Hoops had the most progressive passes* (79 per 90 at 72% accuracy) and deep completions* (8 per 90 minutes).

* A progressive pass  is a one that moves the ball considerably forward while a deep completion is a pass (excluding a cross) that was received within a 20m radius from the opponent’s goal line

Crosses and Dribbles

Bohemians topped the crossing and dribbling charts with 17.2 per 90 minutes (with 31% accuracy) and 29 per 90 minutes (49%) compared with second placed on crossing Derry (17.0 per 90 / 29%) and dribbles St. Patrick’s Athletic (27.7 / 53%).

Kris Twardek and Liam Burt were responsible for the Gypsies topping those charts but we will have a separate article on individual player performance to go up on extratime.com in the next week so look out for that.

Pressing intensity

Bohs were also the team who led the way in pressing intensity. They kept opponent passes per defensive action (PPDA) at the lowest level of any team in the Premier Division.

This is a metric used to measure pressing intensity with the Gypsies keeping their opponents down to just 7.7 passes over 90 minutes.

Losses and Recoveries

Derry City lost the ball less in their own third and middle third of the pitch compared with other clubs and also made the most ball recoveries in the final third of the pitch.

Gareth Southgate: ‘We came here thinking we could win the tournament so tonight is very difficult. It is the best we have played against a major nation during my time but we fell short.'https://t.co/BwahINMYFipic.twitter.com/cWqnv9UQKv

— Extratime.com (@ExtratimeNews) December 11, 2022