Catchers are more susceptible to injury than any other position player.
Javy Lopez and Jason Kendall are perfect examples. If, god forbid, Jason Varitek were to suffer a major injury, I wouldn't want Tim Spehr to be my primary catcher. Scott Hatteberg has proven himself to be a decent receiver and a patient hitter. If the Sox decide it's unfair to keep Hatteberg on the bench when he could start for a dozen other teams, it still makes no sense to trade him now. Spring training tends to be a buyer's market, as the paltry price the Padres paid for Al Martin so clearly shows.