Goalkeepers

How can soccer experts tell that Jan Oblak of Atletico Madrid is the best keeper in the world (assuming that Bayern Munich's Manuel Neuer is rusty or lost something after missing most of last season)?  For that matter, how can the experts tell which goalies are better than others.


Here's my thinking:  Goalie A plays for the team that gives up 2.5 goals per match in the Premier League.  He also has more saves than any keeper because his team's defense is porous and he gets more chances.  Goalie B plays for the team that gives up 0.83 goals per match in the Premier League.  He also ranks at the bottom of the save tally because his team's defense is the best in the league.  Is either goalkeeper the best keeper in the league?  And if not, who is?


Of course there is plenty of empirical evidence about the quality of footwork or not, the quality of the reactions on set pieces, the quality of positioning, and the quality of the pass that starts a counterattack.  And those facts have to contribute.  And perhaps today with all of the cameras and collection of data conclusions are much more than anecdotal -- they are factual.  It would be helpful if the pundits should share that data to provide us with a measuring stick as to why Oblak, Becker, Courtois and De Gea are better than, say, Ederson, Lloris and Buffon.  And if they are better, by how wide a margin?