Some professional athletes have a general sense of when they might get traded, due to the perpetual churn of the rumor mill and the fact that many such players request their trades in the first place. For most inclusions in trades, however, a deal can serve as a major surprise. These so-called throw-ins and make-weights don't have the luxury of anticipating being moved. It's always a possibility, but it can be made reality with little warning.
Rocky Widner/Getty Images