Some Goals Are Bigger Than Others

Not all goals are equal. A last minute winner is clearly more valuable than the 4^th goal in the 85^th minute of a 4-0 win in terms of securing victory. And we can measure that using Expected Points (xPTS).

xPTS is a value assigned to each goal a player scores on the basis that every match (even cup matches) has a reward of 3 points for a win and 1 for a draw. The model assigns that value based on the game time, the current score, and whether you are the home or away team.

For example, a player scoring a 90^th minute goal at home to go ahead by 1 goal in the game would be assigned 1.7 xPTS, the maximum. That is, the number of points the team could be expected to win from that position goes up from 1.1 (the home team would still have the edge statistically in winning at that stage) to 2.8. That player’s goal has added 1.7 to the xPTS. Whilst scoring the 4^th goal in a 4-0 win in the 85^th minute would register as 0.05 xPTS. The goals has barely changed the likely outcome.

Total xPTS

Analysing all the goals Celtic have scored this season, whose goals have contributed the most total xPTS?

Based purely on the number of xPTS attained, you’d expect the top scorers at the top of the list. And indeed there is a strong correlation between the number of goals scored and the number of xPTS earned by each player. Sinclair is the top scorer with 17 and his goals have been worth 8.3 xPts.

xPTS Average

Of course Total xPTS mainly reflects the number of goals scored overall which is partly a function of the number of minutes played. To remove the vagaries of minutes on the pitch, average xPTS per goal is the best method of putting all players on a level playing field. I have removed players scoring less than 4 goals.

As a benchmark, the average xPTS value of ALL goals scored by and against Celtic this season is 0.53.

McGregor’s best moment of the season was the winner against Zenit Saint Petersburg, in the 78^th minute. This earned 1.5 xPTS, and is one reason why he tops the table with an average of 0.68 xPTS per goal. He is joined by another attacking midfielder, Rogic. The Australian is a renowned scorer of important goals – his winner in the Scottish Cup Final against Aberdeen would have been worth the maximum 1.7. All but 1 of Rogic’s goals this season have been worth more than the average 0.53 xPTS. His most impactful was the second away to Linfield in the first game of the season, worth 0.9 xPTS.

It is probably hard for those that score the most goals to maintain a high average. It is to Griffiths credit he is above the average across 12 goals. His highest value goal was the 78^th minute free kick winner away to Ross County, worth 1.15 xPTS.

Dembele hits the average of 0.53 whilst the top scorers both average 0.49 xPTS per goal.

Armstrong is the specialist of the “cherry on top” goal. A pleasing confection but ultimately less impactful on the final result!

What Goals Are Bigger Than Others?

What have been the most impactful goals this season in terms of securing the points? These are the goals that have been worth the most xPTS in Celtic matches and could be said to have had the biggest potential impact on the result.

McGregor’s winner in the 78^th minute in the Europe League is the highest scoring goal by this method, worth 1.5 xPTS. This is the highest value goal in any game this season.

For the opposition, the own goal by Lustig conceded at Motherwell in September had the highest xPTS against. Yet Celtic rescued a point with a late penalty (won by McGregor).

Note that Tierney’s goal away at Aberdeen has the second highest xPTS. The second goal in a game, especially one so late (83^rd minute) is often decisive.

Some Goals’ Assists Are Bigger Than Other Goals’ Assists

Heaven knows you’re miserable now with me flogging this theme to death. But one more comparison is the players that have provided the assists. Let’s call it xPTSA! I’ve removed those with less than 5 assists.

Ntcham leads the way in setting up potentially the most impactful goals. His most valuable assist was setting up Griffiths for the 2^nd goals against Dundee on 26^th December, worth 0.9 xPTS.

The most prolific assisters are bunched around the average of 0.53 mirroring what we saw with scorers – the more goals you score the more likely you are to be near the average xPTS value.

Mulonda set up the goal with the highest xPTS of the season, for McGregor against Zenit (1.5 xPTS), and that was his only assist (so far!).

Although Griffiths, Rogic and McGregor have scored the goals with the most xPTS, they have provided the chances with the least!

Oh, I say – time for that crate of ale.