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by ChelseaStats

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OhDennisWise - Mata's magical performances are more reliable than his stats

What constitutes an assist is debatable, a common area for confusion and discussion. This article will try to explain the method to the madness and aim to be a focal point for future debates.

I was asked on Twitter how many goals and assists Mata had recorded in all competitions this season. 18 and 25 respectively, at the time of writing. Here’s a typical response during the conversation (see other here, here and here):

Opta, a major sports data provider, but by no means the be all and end all of football statistics, states a goal assist is “the final pass or pass-cum-shot leading to the recipient of the ball scoring a goal”. Very definite terms are used: a pass or pass-cum-shot. So winning a penalty, winning a free-kick, or a deflection off a player’s backside doesn’t count unless, of course, the backside in question displayed significant intent!

In the frozen world of Ice Hockey, the NHL handle assists completely differently. An assist is awarded to the last two players to touch the puck prior to the goalscorer, whether the scorer is on their team or otherwise. Occasionally an assist is awarded to just one player if there is no secondary player involvement. Other sports are slightly convoluted and a tad misleading. Bear with me, we’ll revisit this in a minute.

The Premier League use a variety of sources and tweet who assists are awarded to for each goal in each of their league games. They often award the player to touch the ball before the goalscorer or the player fouled to earn a penalty or direct free-kick (that had been successfully converted). These stats are generally aimed at the “fantasy football” audience, where points are accumulated for the build up to a goal. If only goals were rewarded, everyone would pick Lampard but choose Baines (who takes penalties and free kicks) over Cole!

Is it fair for a player who has been tackled, felled from behind, to be awarded an assist? Could a player earning a penalty step up and take the penalty to assist himself? How can a long clearance up field be an assist (e.g. Cole clearing the ball against Barcelona, resulting in Torres scoring)? Despite being the best left-back in the world, I’m 99% sure it was not intentional. There is no way that could have been anything other than good fortune.

Whether data is wrong is sometimes by-the-by, but as long as it is consistent, it enables comparisons to be made. As a former data analyst, now web developer/designer and slightly obsessive compulsive nerd, with acute insomnia, consistency is very important. Context is also important, when “statting” all competitive fixtures, including the Champions League, the European Super Cup and the World Club Cup, as well as the domestic league and cups.

A line has to be drawn to identify the boundaries in statistical analysis, and to be able to interpret these boundaries. All the assist information stored in the TheChels.co.uk database is provided by those best qualified, the analysts that find correlations, causations and insight into the game, ensuring data is to a standard they can trust. Going back to the hockey, it’s not misleading because fans are more aware of the definition and how it works. It’s consistent in each goal, game, season…

Mata has 18 goals and 25 assists in all competitions this season, based on my data.