Pitcher is used on a day off.
 

I just noticed watching my team in the final series Irl.170 that the game treats a day off as a day pitched and moves to the next pitcher in the rotation. Not sure if this has been discussed before but ir could be critical to know if your in a crucial game and there is a day off because of switcjing home teams.

Pine Tar

Well, they select a new starter sometimes because a guy that was only 70% or so rests on that off day and gets to 100% and is the ideal starter now...the game doesn't switch until the off day is simulated. However, a few other quirks in starting pitcher selection HAVE been experienced (personally) & reported by others now & then.

Something similar happens with lineups sometimes. One player suggested using the 7-day lineups (which can act like a virtual lineup card) to avoid these mistakes.