Is the 13 pitcher limit in effect starting May 1? If so, they need to remove two pitchers.
The only two pitchers with options that make sense are Milner and Gustave. I think they'd ideally like to have a roster spot or two to shuffle between all the 40-man pitchers with options. That will inevitably occur with some kind of injuries, but if they value the most roster flexibility immediately, Urena may be the odd man out. Would be a tough break given he's pitched well enough to be on the roster.
Whether they can send one down for May 1 or not until Urias comes back, Brosseau or Hiura has to be the position player out. Peterson has been bad offensively, but being a versatile LHB without options, he's got a longer leash.