Just like Iker Casillas is much more experienced than Keylor Navas.
With that logic, Iker should be the better GK which he is not.
You are going to extremes, but ok.
It would be easier to imagine 2 skills:
1. player's skills
2. experience
-- your skills can go from 1 to 100% (100% is the maximum, of course)
-- experience can go from 1 to 100% also
-- in the first 100 matches in La Liga, you will learn the most (for example, 50% of your total experience)
-- in the matches number 101-200, you will learn slightly less (for example, 30% of your total experience)
-- in the matches number 201-300, you will learn less and less (for example, 10% of your total experience) etc., because you have already learned more or less everything you will need as a player
-- so, the difference between 400 La Liga matches played and 300 La Liga matches played is much smaller, than between two players when one has 100 matches played in La Liga, and the other has 0 matches played...
-- so, on example, it would look roughly like this:
-- Ter Stegen skills are at 98%
-- his experience is at 50%
-- Bravo skills and abilities in general are weaker, and he skills are at, let's say, 90%
-- but his experience is at 90% also
-- Masip, his skills are at, let's say 80-90%
-- his experience is more or less at 10%
-- Pinto has weaker skills as a Gk, let's say 70%
-- his experience was around 80%
About your Casillas vs Navas:
-- Casillas has skills at (let's say) 80%, he is not at his prime anymore, he is much weaker than in the past
-- his experience is at 100%
-- Navas:
-- his current skills are at prime, let's say 97-98%
-- his experience is around 80% (60 NT matches for Costarica)
Anyway, I was giving percentages just as an example. But for all players, skills are probably 70% of his abilities.
And experience is another 30%.
Young player can play if he is awesome in skills. Then he can compensate his low experience with world-class skills (Young Messi)
If a young player is just average in skills (let's say Montoya, imo), then average skills+his very low experience is the reason why he is on the bench always.
About Casillas and older players, there is a moment when his skills are starting to go down, and when his huge experience doesn't help him anymore.
The best players, are of course, those who are in their prime in skills and also have enough of experience already (200+ matches, let's say)
For example, Alba, Pique, Busquets, Rakitic, Iniesta, Messi, Neymar, Suarez, from our current players.
