Losing someone like Aaron Thompson, were that to happen, would be only a minor matter - he's probably cut at the end of the season anyway. Of more importance is that Berrios does not yet need to be protected from rule-5 next December.So having him on the 40-man immediately means someone else doesn't get protected. Berrios can be added to the 40-man next year at whatever point he makes the team. Adding him now would add up to a lot of trouble, in return for a very speculative benefit to this year's post-season push.