My son had a high school coach were the next thing he learned about pitching would be the first thing he learned. There wasn't a pitching coach when my son's varsity career started (soph year).
My son was a reliever. He could come in and throw hard strikes. He often had to do it coming from his field position. The coach never put him on the mound to start an inning. He always waited until the barn was on fire. Every pitch was a stress pitch.
On day in 20 something degree windchill the coach came to the mound and handed the ball to my son. My son handed it back. My son told him he would be happy to leave the game for one hitter, warm up and return to the game. But he needed time to do his blood flow and stretching exercises and throw a few pitches on the sidelines. My son was able to say this to the coach because I had a conversation with my son on things you do and don't do as a pitcher. Before the season he told the coach if it's possible he's going to the mound tell him between innings so he can get loose. It didn't happen this day. He was never told it might be possible he would pitch.
The coach gave him a dirty look and gave the ball back to the pitcher. He didn't have much to say to my son for a few days. There were also other short term consequences. He sat him for a game for not being a team player. But the coach got over it.