The other possibility - if they feel they have enough without bringing anyone new to the 40-man - is to just DFA Holladay today, knowing they'll be bringing up Vazquez as the 3rd catcher. Given we don't really know their evaluation of the 2017+ potential and thus vulnerability of Noe, Owens, Elias, Cuevas, Jerez, Abad, Hembree, Brentz, Marrero and Hernandez, we can't really rule any of them in or out. If they want to be conservative and keep their options open however, they can keep all those guys and only lose Holladay.
The bullpen available right now is:
RH
Kimbrel (25)
Buchholz (25)
Kelly (25)
Ziegler (25)
Barnes (25)
Tazawa (25)
Uehara (DL15)
Workman (DL60) - is he rehabbing yet or done for the year?
Hembree (40)
N Ramirez (40)
Cuevas (40)
LH
Ross (25)
Scott (25)
Abad (25)
Owens (40)
B Johnson (40)
Elias (40)
(obviously I know there's no 25-man but only a 40-man for the rest of the year but I'm using '(25)' to denote those on or who have already been called up to the MLB club.)