Quality/skills

[Toxcatl]

Highlighted (white) skills are key abilities, and they are more important that non-key abilities.
Average doesn't mean much by itself, because P&M contains both key and non-key skills.
Therefore, if you have two players of the same quality, the one who has key abilities higher and non-key abilities lower is better. Well, he should be theoretically, but that's not guaranteed: many of us believe that there is a hidden parameter that determines players performance along with Quality, but this is another story.
Note that if a player has several positions, he has key skills from all of them. But on every position he will use mostly (only?) those skills that are highlighted for this position. For example, if you have MC/AMC and you use him on AMC position, he doesn't need defence skills although they are highlighted.
You also should know that key and non-key abilities have different pace of training. More info here:
https://forum.topeleven.com/top-elev...tml#post438035

Player's Value is important too, because it gives you a glimpse of another hidden parameter (Talent) that determines how fast the player gets XP. But again this is different, the third one, story.