To generalize a bit, some of the value a shooter provides comes from taking more and better shots (e.g. taking them closer to the goal, at a better angle, amid fewer defenders, etc.), and some of it comes from putting in those shots more often. For example, Messi’s typical regular (non-set piece) shot comes from 14.9 yards out, while Ronaldo’s average shot comes from 20.1 yards out. ESPN/TruMedia has a model for estimating the chances of a player making each shot he takes based on type and location (this metric is known as expected goals). The difference between a player’s actual goals and his expected goals is called “goals above average” (or GAA). Because Messi takes shots that are more likely to go in, his average attempt has an expectation of .182 goals, while the average Ronaldo shot has an expectation of .124 goals — so we would expect Messi’s shooting to be more efficient based on that alone. However, Messi has also exceeded that expectation by a greater amount than Ronaldo has. Messi scored .220 goals per shot attempt for .038 GAA per goal. Ronaldo scored .139 goals per attempt, so he had .015 GAA per goal.

Lionel Messi Is Impossible | FiveThirtyEight Monday, July 7, 2014 @ 9:57pm