10 players

[Pez]

So I never played organized football or anything, what are the operational aspects involved that resulted in us having 10 players on the field?

When they call a defense, do they hold up signs or somesuch so the right personnel gets on the field?

There were 10 guys on the field, each of which could have called a timeout, and Steichen who could have called a timeout.

I cant imagine that Franklin wasn't looking around and saying, "oh hey, this looks weird..."

How does it actually work such that a mistake like this happens?