Irvin had a 1-2-3 seventh inning in DC and Morgan has looked good in camp as well. I agree that they have several other LH relievers that they are high on, so that probably was the final factor in parting ways with Liriano. He is likely to catch on with another club, if not to start the season, then soon after.
I really have not gone through the list of pitchers to try to predict the 11 who will be in the bullpen to start the season. Nola, Arrieta, Wheeler, Eflin, and Velasquez seem set as the starters.
For the five bench players, I predict Knapp, Walker, Haseley (when Quinn starts), Harrison and Garlick. Phil Gosselin has been impressive (5 hits the other night in scrimmage and a double in Washington in his only AB) and could be a valuable bench player, so he could take one of the slots. I included Walker in my five because I read today that he has been told that he has a 30 man opening roster spot. Otherwise, I would have added Gosselin.