I love it when your opponent has never learned, after a decade of playing fantasy baseball, that two-start pitchers rarely win the game for you. If a pitcher is projected to win 10 games in a year, and you've got him on a double-start OR you have another decent pitcher going up against a really terrible team, you go with the single-start guy with the better chance of winning one game.
In a 22-week season, where your pitcher is going to get 30 starts, expecting him to win two games in one week when he's a mediocre pitcher to begin with is foolish.