Maybe 100-200? But we’ll never know, no one will play an opening they don’t know at all.
If one played an opening which he did not know, his playing strength would drop by how many Elo?
I have done this before.
Multiple times!
My rating dropped 100 points only, but I also did steady regulation.
The important thing to remember is you are in control of the line you play.
You can always switch back to make sure your points don’t plummet.
For Example:
I use to play the Italian Game.
I played the Italian Game from rating 500 to around 1,500.
When I reached round 1,500, I wanted to change to Ruy Lopez.
So I started playing the Ruy Lopez.
My rating started to drop as you would expect due to the fact the line was new to me.
I would lose points, but I wouldn’t ever go below 1,400.
The reason why is because when I got to around 1,400. I would just go back to playing the Italian Game for few games.
Remember, No one is forcing you to play 1 line nonstop.
Learning a new line is a process and you don’t have to rush it
Than I
If a player was suddenly forced to play a sound opening which he has zero knowledge of (an opening which he never studied and never played before), his playing strength would drop by how many Elo points?
His playing strength would drop more if it was a sharp tactical theory-heavy opening than if it was a slow positional opening.
It depends on the strength of the player. A 2000+ rated player probably wouldn't have many issues and their overall strength isn't going to be impacted.
For a sub-1000 player, it's also unlikely to have any impact.
If a player was suddenly forced to play a sound opening which he has zero knowledge of (an opening which he never studied and never played before), his playing strength would drop by how many Elo points?
His playing strength would drop more if it was a sharp tactical theory-heavy opening than if it was a slow positional opening.