When he gets warmed up, they tend to not want to sit him. I don't know why, maybe someone with physiological background might explain what happens if you get a guy up and then don't use him. Wood with his starters background and arm injuries takes a little longer to warm up. So if they get him warmed up, he's already thrown enough pitches and put enough stress on the arm that even if they sit him down, they can't consider it an "off day" in their bullpen usage. So it makes more sense to go ahead and throw him in the game instead of also using up an off day of another reliever. even if you can't consider it an off day, you can still spare your second-best bullpen arm from throwing pitches in a game situation when the outcome is virtually decided. the cubs are going to need woody in october; best to keep the mileage off his arm if you can.