Off script

off script

So, how did your team get on in the first round of Premier League fixtures for the 2019-20 season? My team, Sheffield United, were back in the top flight after a 13-year absence. It didn’t go too well though. Here’s the report:

EFL goal machine Billy Sharp’s long wait for a top-flight strike ends on the opening day. Ravel Morrison with the assist. But Bournemouth run out 4-1 winners.

And as if that’s not bad enough, we finished the season in bottom place:

script

Disappointing, but maybe not unexpected.

Arsenal also had a classic Arsenal season. Here’s the story of their run-in:

It seems only the Europa League can save them. They draw Man United. Arsenal abandon all hope and crash out 3-2. Just as they feared. Fans are more sad than angry. Once again they rally. Aubameyang and Alexandre Lacazette lead a demolition of high flying Liverpool. But they drop too many points and end up trophyless with another fifth-place finish.

Oh, Arsenal!

But what is this stuff? The Premier League doesn’t kick off for another week, yet here we have complete details of the entire season, match-by-match, right up to the final league table.

Welcome to The Script, produced by BT Sport. As they themselves explain:

Big data takes on the beautiful game.

And in slightly more detail…

BT has brought together the biggest brains in sports data, analysis and machine learning to write the world’s first artificial intelligence-driven script for a future premier league season.

Essentially, BT Sport have devised a model for match outcomes based on measures of team abilities in attack and defence. So far, so standard. After which…

We then simulate the random events that could occur during a season – such as injuries and player transfers – to give us even more accurate predictions.

But this is novel. How do you assign probabilities to player injuries or transfers? Are all players equally susceptible to injury? Do the terms of a player’s contract affect their chances of being sold? And who they are sold too? And what is the effect on a team’s performance of losing a player?

So, this level of modelling is difficult. But let’s just suppose for a minute you can do it. You have a model for what players will be available for a team in any of their fixtures. And you then have a model that, given the 2 sets of players that are available to teams for any fixture, spits out the probabilities of the various possible scores. Provided the model’s not too complicated, you can probably first simulate the respective lineups in a match, and then the scores given the team lineups. And that’s why Sheffield United lost 4-1 on the opening day to Bournemouth. And that’s why Arsenal did an Arsenal at the end of the season. And that’s why the league table ended up like it did above.

But is this a useful resource for predicting the Premier League?

Have a think about this before scrolling down. Imagine you’re a gambler, looking to bet on the outcome of the Premier League season. Perhaps betting on who the champions will be, or the top three, or who will be relegated, or whether Arsenal will finish fifth. Assuming BT’s model is reasonable, would you find the Script that they’ve provided helpful in deciding what bets to make?

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Personally, I think the answer is ‘no’, not very helpful. What BT seem to have done is run A SINGLE SIMULATION of their model, for every game over the entire season, accumulating the simulated points of each team per match to calculate their final league position.

A SINGLE SIMULATION!

Imagine having a dice that you suspected of being biased, and you tried to understand its properties with a single roll. It’s almost pointless. Admittedly, with the Script, each team has 38 simulated matches, so the final league table is likely to be more representative of genuine team ability than the outcome of a single throw of a dice. But still, it’s the simulation of just a single season.

What would be much more useful would be to simulate many seasons and count, for example, in how many of those seasons Sheffield United were relegated. This way the model would be providing an estimate of the probability that Sheffield United gets relegated, and we could compare that against market prices to see if it’s a worthwhile bet.

In summary, we’ve seen in earlier posts (here and here, for example) contenders for the most pointless simulation in a sporting context, but the Script is lowering the bar to unforeseen levels. Despite this, if the blog is still going at the end of the season, I’ll do an assessment of how accurate the Script’s estimates turned out to be.

 

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