1.The autorest # appears to be most important.
2.Available for relief checkbox.
3.The 'Rest' setting.

Just had my Jack Quinn throw 160 pitches and is out for the season. He was on rest and didn't have his 'available for relief' checkbox checked, but he was at 97%. My mopop, who I wanted to come in the game, who was available for relief, who was set to 'rest' didn't come in because I didn't turn off the autorest. Hope that helps someone.

I've had my autorest set at 10% for my mopup and put him on rest but that didn't work. My mopup was called into the game to close and of course blew it. Autorest may have been the key in that situation. It was set too low permitting him to pitch despite being set to "rest". Different than what happened to you but it does support your statement #1.