1) His ability to convert shooting opportunities has nosedived
Non-penalty goals – xG gives us a good bearing as to how well a player is performing in front of goal. If their number of non-penalty goals is below their xG number, they will get a negative score, and if their number of goals is above their xG, it will give us a positive number.
Over the last four years, Griezmann has gone from +5.9, +2.3 and +1.3 to -0.8 last season. It means his ability to convert goal-scoring chances has progressively got worse.