Well, the callups need to be on the 40 man, and you need to use caution before you add someone to the 40 man. Remember, the Rule V is in December and every yr, there are guys who need to be protected. Just 2 yrs ago, the Yankees didnt protect Nova and lost him for spring training to the Padres. Glad they didnt make the same mistake this yr. And, this yr, the Yankees lost a good looking reliever in Kanekoa Texeira to the M's who subsequently moved him to the Royals. He looks like he could be a good piece too. Every decision has a reaction, so one needs to be cautious when calling kids up.
Right now, the sox have plenty of guys on their 40 man. I would expect Bowden, Richardson, Wagner, Iglesias, and Reddick to be called up.
Then you have to look at guys who will need to be protected for 2011. Lars Anderson, Luis Exposito, Jason Rice, and a few lesser guys. So, it might be beneficial to add Lars now and bring him up. But for Rizzo, you'd be adding a player before they need to be protected