Depth?
Youk was a third baseman pretty much all of his Minor League Career. No one (except me, heh) thought he would do anything more than a half-decent job at first base. Most people figured JT would be playing two or three games a week.
Now Youkilis is batting .310 with 21 RBI and is among the top ten in OBP and pitches per at bat, as well as making Gold Glove plays at first.
Defensively, Youk has had 150+ career chances to make an error at first and HAS NOT MADE ONE YET.
Hee-Sop Choi is a better offensive pinch-hit option than JT Snow, a notoriously mediocre hitter. If Youk does get hurt for a week, then we have Hee-Sop Choi, who is decent enough offensively to figure in a game, and good enough defensively (a la Doug Mientinddfgdwicz) to not be a liability. If LOWELL gets hurt for a week, then Youk can take third and Choi can take first with the same results, as Youk can play third just as well as hes been playing first.
JT Snow can do the exact same thing as Choi, except hes a liability at the plate. He may have six Gold Gloves, but six Gold Gloves arent really nessecary for a player in the position that JT or Hee-Sop are here for. Send JT where he can get the playing time he deserves.