There is no such thing as a medical redshirt, an injury would be put through the athletic dept as a waiver to get the year of participation back and also depends on length or seriousness of injury. The term redshirt applies to a grade designation and not an official term of the NCAA.
All it means as an example, a redshirt freshman is an academic soph who is in first season of participation.
Keep in mind that the NCAA allowed everyone who played last year another season and some coaches don't even know what to call it. Lol.
Under a new rule a freshman can play up to 4 games and not lose that first year of eligibility.
Yes, thanks.
As someone else posted, redshirt simply means being enrolled as a student and not playing in order to save a year of eligibility.
Usually this is done by design, but I know of a player who got injured very early in the season and was forced to sit out for the rest of the year. Not in football. The player applied for and was granted the extra year as a medical exception.
I thought of this as the OP specifically asked about redshirting after playing in a regular season games.
So I guess to answer the question fully - the only things that have triggered an extra year of eligibility after playing in a game are a significant early-season injury, the specialness of being a D1 freshman football player, and covid.
Anyone know of anything else?