Fresh terminology has worked its way into the language of football and is being deployed by coaches, pundits and fans alike, but what does it mean? We are often told that football is a game of opinions and that is true to an extent, but the increasing sophistication of statistical analysis in sport has sharpened the picture. A term that has crept into the everyday lexicon of football media - and, as a result, the wider football-watching audience - is 'xG', which emerged from research of particular moments in games. Thanks to 'xG' it is no longer sufficient to casually suggest that a player should have done better with a chance when they miss - there is now data to back that argument up, or, indeed, to rebut it.