BLOG Advanced metrics: Expected assists19 December 2017
I’m sure by now you’ve all seen expected goals used in football media, whether that be during Match of the Day, Monday Night Football or by pundits, presenters and experts across TV, digital and print media. If you haven’t you can check it out here.
At Opta we strive to bring innovative ideas that can be applied to add further context to the game that we all know and love. One example of this is comes from our series of advanced analytics - expected assists.
As we all know an assist is the final pass that leads to a goal, however that player is reliant on their teammate scoring; if a shot is missed the player, making the pass doesn’t get credit an assist.
A player could make several passes into the box, creating good goalscoring opportunities, but not be rewarded with an assist due to the striker not finishing these chances. On the other hand, a player would be rewarded with an assist by making a simple pass from their own half with the striker going on to score.
Analysing millions of passes, Opta created its expected assists model which gives all passes a likelihood of becoming an assist and can give further context around the players that are passing the ball into dangerous areas that aren’t getting rewarded with an assist.
A good example of this is Alexis Sanchez. Sanchez has seemingly been in average form for Arsenal but when we look at his underlying expected assist numbers we can see that he is playing well. With 4.74 expected assists, and his actual assists coming in at 3, means he is creating chances that should result in 4.74 goals and can point to poor finishing as to why he doesn’t have more assists.
The metric can also be used to see some standout creative players across different divisions. Malcolm of Bordeaux has been having a breakout season and has been linked with a host of big teams. His xA per 90 is 10th in Europe and he’s actually slightly underperforming his xA overall (5.5 vs 4 actual assists). At 20 years old this is a remarkable number for someone his age and suggests he is a player bigger teams will look to secure the signature of.
Posted by Edwin White at 15:51