Answering your question instead of sending people to my sheet...
Both were throwing 3X a week two months ago. I bet they are both 60 day candidates. Even if close to ready, you have 30 days on rehab assignment (60 days in SGL's case because of the special TJ rule), so if they are close for game action by late April, you are covered.
Mattson could also theoretically be IL'ed, but that starts his service clock unnecessarily. They did this with Freddy Pacheco a couple years ago, but he was claimed too late to be optioned, so it was the only way to keep him .