What is the TransferRoom Player Rating?

The TransferRoom Player Rating is a 0-100 score that values a player’s ability on the pitch.

Broadly, a player's rating takes into account:

• The quality of the team he plays for (Squad Ratings)
• How regularly he plays (Percentage of available minutes)
• The standard of competition he plays against (League Ratings and statistic conversion rates)
• His individual performance statistics, weighted by the stats most relevant to his position
  
  

We calibrate Player Ratings so that the combined performance of the players in a squad is predictive of that squad’s rating. Or in other words, the players contributing the most on the pitch for the best squads receive the highest ratings.

The TransferRoom Player Rating has existed since summer 2021, powering both xTV (Expected Transfer Value) and the intelligent recommender system on the platform. We’ve continually revised and updated the methodology, and in August 2023 we started displaying the rating itself to help clubs and agents make a faster initial assessment of a player’s ability when using the TransferRoom platform.

Squad Ratings

The first step is to calculate global squad ratings. We start by taking all domestic league matches over the last three years, and assess the result of each match based on three criteria:

• Goals scored (the result)
• Expected goals scored
• Non-shot expected goals: a model of the match based on possession and dangerous passes
  
  

We run through every match in order, using a technique calling “Bayesian updating” to calculate squad ratings within each domestic league. We give more weighting to more recent results e.g. a match yesterday is more important to your squads’ rating than a match two years ago.

To go from domestic to global ratings we calculate conversion rates. These are uplifts or handicaps for teams in each league based on how teams in that league typically perform versus teams from other leagues. We do this by analysing cross-competition matches in the same way as above, such as continental and cup competitions. 

This process allows us to merge the squad ratings for each league into a global ranking system based purely on the on-pitch results of each team.

Simple Ratings

At this point we can calculate “simple” ratings for each player, based solely on the rating of the team(s) they have played for and the percentage of available minutes they have played. Both of these are weighted so more recent matches are more important. By doing this we are calculating the contribution of each player to his squad’s rating. This works well because the best squads (generally) have the best players playing for them, and vice versa. 

While this approach captures a lot of useful information, there are obvious flaws. The best players on a team don’t always play more often than their teammates, and certain positions typically play more minutes than others e.g. Goalkeepers and Centre Backs will usually play more minutes on average than Wingers. 

Performance Data

Clearly there are lots of other performance metrics to assess a player’s contribution to his squad’s rating that go beyond minutes played. There is a long list of available statistics; xG, xA, aerial duels, pass accuracy, high pressing recoveries, ball losses, etc.

To effectively incorporate performance data into our ratings we need to address two areas:

• How do metrics convert across competitions? E.g. what is better, 0.8 goals per 90 in the Eredivisie or 0.6 goals per 90 in the Bundesliga? 
• How do we weight each metric - i.e. which metrics are more important than others for each position?
  
  

To deal with this, we have built conversion rate models to estimate the value of each metric in each competition. We do this by analysing player performances before and after a transfer between two leagues. For example, Darwin Nunez averaged 0.58 xG per 90 in the Primeira Liga in 2021/22, and 0.48 xG per 90 in the Premier League in 2022/23. This is evidence that xG in the Premier League is more valuable than in the Primeira Liga. Our analysis looks at thousands of transfers to build conversion rates for each metric, and is constantly updated to react to changes in relative competition quality.

We then build a model to predict each player’s contribution to their squad’s overall rating, based on their competition adjusted performance data. We do this separately across different positions, to reflect that different roles have different measures of success on the pitch. For more detail on metrics used per position, please see the FAQs below. This model gives us the relative weightings of each metric in terms of their importance toward winning matches. Applying the model to each player’s performance data gives a data-driven rating for each player.

Putting it all together

Final TransferRoom Player Ratings are a blend of a player’s simple rating based on minutes played and squad level, and the rating derived from their performance data. We adjust these to be between 0-100 to make sure they’re quick and easy to understand.

Frequently Asked Questions

Which metrics are important for each position in the TransferRoom Player Ratings?

For every position, the average squad rating of the team(s) a player has played for, and the percentage of available minutes they have played are important. Each position is also evaluated on a large number of performance metrics, with the main metrics per position listed below, in rough order of importance. 

All metrics are adjusted for the standard of competition and standardised. They are evaluated per 90 minutes, as a percentage, or otherwise adjusted to remove opportunity bias.

GK - goals conceded, xG conceded - goals conceded, pass success, progressive passes, aerial duel win rate

CB - defensive duels win rate, progressive passes, interceptions, aerial duel win rate, xG

LB, RB - successful passes to the final third, xA, defensive duels win rate, progressive passes, pressing ball recoveries, progressive runs

DM, CM - xA, successful passes to the final third, pressing ball recoveries, interceptions, progressive passes, progressive runs, defensive duels win rate

AM, W - xG, xA, finishing ability, successful passes to the final third, pressing ball recoveries, progressive passes, progressive runs

FW - xG, xA, finishing ability, successful passes to the final third, pressing ball recoveries

Can I compare ratings across different positions?

Ratings are calibrated based on the impact a player has towards winning matches and improving their squad’s rating, so they are comparable across positions, e.g. an 80 rated CB has the same impact as an 80 rated AM. However, different positions are valued on different metrics, and of course a blend of different positions and skills are required in any team, rather than simply the 11 highest rated players available.

What is the minimum number of matches a player needs to get a rating?
Players must have played at least 500 minutes of senior domestic league football over the last 2 years to receive a rating.

TransferRoom Player Ratings incorporate minutes played as an input. Does that mean a player’s rating will go down if he is injured or suspended?

The input we use is % of minutes played when available, rather than absolute number of minutes played, so we don’t punish injured or suspended players. The important indicator of ability is how often a player is selected to play when they are available for selection.

Is there any bias against younger players, because a shorter career so far means less opportunity to get minutes, goals, assists etc?

We use % of minutes played when available, and all performance stats are evaluated per 90 minutes or as a percentage so players who have played fewer minutes are not disadvantaged, as long as they meet the minimum threshold to receive a rating. 

However, older players who are still playing regularly at a certain level tend to be good players, simply because they need to be good to maintain that playing time. We are analysing up to 3 years of performance, albeit more recent matches count more. But someone who has been good over that period will have a good rating.

Younger players of course have higher “potential” - it is more likely they will improve in the future than an older player. Therefore they usually are more sought after in the transfer market and have a higher xTV than older players.

How will a player’s rating be affected by changing club / league?

As metrics are adjusted for competition level, Player Ratings will not change purely because a player changes club or league. Of course if a player improves / declines and as a result moves to a better / worse club, then this change in performance will be reflected in their rating.

How does the TransferRoom Player Rating relate to xTV?

TransferRoom Player Rating is one of several key factors in a player’s xTV. All things being equal, a player with a better rating will have a higher xTV. However, other factors including Age, Contract length, and economic status of their parent squad are also very important to xTV (amongst many others).

How often are ratings updated?

We update TransferRoom Player Ratings at the beginning of each month.