Well, Zumaya was a starter before last season, while Meredith didn't have a roster spot in Boston and wasn't given the luxury of Petco until mid-way through the first-half of last season. That's why those two weren't on any lists. Broxton had walked 12 in his 13 innings above AA before last season, so it was rather unheard of for him to have the success he did last season.
As far as the guys who can be this year's Broxton, Zumaya, or Meredith are, it really is still a guess. I guess, from the track record, look at young minor league flame-throwing starters on teams that may need bullpen help.