I was thinking more "10 to 20". I suppose from person to person and at different stages of life the filter of who is appropriate for your playing field might change. . but even 10^2 seems high. I can barely name 20 critically important people in my life let alone those which are on my playing field. I have managed this, a bit unconsciously. Generally when my field is managed in line with my conscious values I'd only regard a person who I know and respect professionally. Further filtering on whether I actually feel like I personally (not just professionally) know the person.
curious what a different playing field mechanism might be described as
The monkeysphere is "how many people you can comprehend as people with their own full lives", and is on the order of 150-300.
"Critically important" in your life is a far higher bar, so 10 to 20 makes sense.
"Playing field" is a far lower bar where only the relevant metric matters, which widens the range to a far larger number of people.