What I mean is, is the player in question good at his position or not. If you compare Duran to Yoshida alone (ie in a vacuum) for example, you could conclude Duran is a great outfielder. If the Yankee LFer sucks and you compare Duran to him alone, same conclusion. Does that mean that Duran is an outstanding LFer? Unknown-because you have to compare him to the other players who play that position at the same level.
You certainly can compare two players at the same position and conclude that one is better than the other, but both may be excellent or both may suck. It’s much more useful to compare a player to all other players at that position.
So when SS wrote that “you should check out the Yankee LFer” in reference to how good or bad Duran is there it’s not meaningful because both may be excellent or both may be horrible. If both suck you can look at the Yankee LFer but if Duran sucks (I don’t think he does) then he sucks.