Why don't they use their ace during the week? Do you get double bonus points for winning a weekend game?
Because the weekend is when all conference games are played OR in the case before conference play starts they play a 3 game series with someone. Once they get the rotation set, they want to keep it with the same number of days off between starts.
This week of course, the confernece starts Friday. No way you want to waste your ace on a non-conference game.