You're right, kind of. "Four years" I think translates as "four Rule 5 drafts exposed to", which would make them both eligible next year. if Rivas counted as 19 when he signed, or Aguilar next year and Rivas in 2010, if Rivas counted as 18. I was counting from 2006 for Aguilar, forgetting that he didn't play the year he was drafted.