Analysis: The Europa League and the Thursday Night Effect
It's a received wisdom that teams that have to play midweek European games are at a disadvantage when it comes to league games the following weekend, but just how much of an effect does continental participation have on performance?
“The Europa League takes an even bigger toll [than the Champions League] in my opinion, that's the problem,” said Harry Redknapp in April 2011
. “That Thursday night one, every week, and playing Sundays every week.”
It’s hard not to see his point; virtually all teams involved in the Europa League get two days rest between their European match and following domestic league fixture. Champions League teams may get up to four or even five days.
But do these supposed disadvantages hold true in reality? To test this received wisdom, Prozone analysts have looked at how teams playing on Thursday nights in the UEFA Cup and Europa League have performed relative to expectations on the following Sunday.
We set expectations based on historical betting data from football-data.co.uk
. Bookmakers’ odds add up to more than 100%, but we can normalise these odds to give us the probability of a home win, away win and draw.
From these probabilities we can estimate expected points for both teams. As an example, we will use a game where Team A has a 60% chance of winning, Team B a 10% chance of victory and a draw 30% chance. Therefore, the expected points for Team A is (3 x 0.6) + 0.3 = 2.1 points, and Team B (3 x 0.1) + 0.3 = 0.6 points. From this calculation we can state that, statistically speaking, if the same match was played hundreds of times, Team A’s average points from these games would be 2.1 and Team B’s 0.6.
Over time, we would expect teams to score as many points as would be expected. Any difference between actual points and expected points is known as residual points.
We can now compare actual and expected points on Sundays for teams who played on Thursdays in Europe. One of three outcomes is possible:
1. If there was no effect of playing on Thursday and Sunday, actual points would be roughly equal to expected points, giving us a residual of zero.
2. If there was a negative effect of playing Thursday and Sunday, we would expect a negative residual: teams collecting fewer points than expected.
3. If there was a positive effect of playing Thursday and Sunday, we would expect a positive residual: teams collecting more points than expected.
It turns out that the second outcome holds true: teams consistently drop points when playing on Sundays after Thursday European matches.
In 215 league games after Thursday European matches since 2001, teams have scored over 38 points fewer than would be expected. The effect is particularly pronounced after European away matches, where teams have scored 32 points below expectation.
Another way of looking at this is that for approximately every three Thursday European away matches, teams drop one point on the following weekend. After home games, it’s only one point dropped every 18 weekends. This makes basic sense, as travel is likely to have a detrimental effect on performance.
For the purposes of the study, Sunday matches between teams that both played on the preceding Thursday have been excluded.
There is some variation by team, too. Curiously, Redknapp’s former team Tottenham have actually scored more points after European games since 2001, but it seems unlikely that this will hold over time.
Two teams in this year’s competition – Liverpool and Newcastle United – have had unfavourable histories with the competition in terms of the effect on league form. Nine of the 12 teams dropped more points after away matches in Europe than after home games.
A few points to consider:
- The teams analysed did not systematically drop points in league matches not following Thursday European matches.
- Betting odds are a good way to set expectations for results, but can be influenced by the volume of bets placed.
- The odds may not reflect team selection. For example, Middlesbrough and Fulham may have selected weaker teams in a bid to sustain their European runs, leading to a negative points residual.
We’ve already seen Newcastle and Liverpool field supposedly weaker teams away from home in the first round of group matches this season. As teams qualifying for Europe’s second-tier competition look to push for Champions League places through league results, this may be a sign of things to come.
This post was originally written by Prozone Statistical Analyst Omar Chaudhuri for his analytics blog, 5 Added Minutes.