The starting pitching depth has been greatly improved with the additions of Max Castillo and Kolby Allard. Both have an option and likely will join Nick Nelson in the AAA rotation. They, along with Mick Abel, Griff McGarry or another break out starter at AA or AAA, provide reasonable depth for the projected 5 starters.
I expect that DD will add someone to the bench mix and the bullpen mix, but would not be surprised to see additions that have option(s). If there were a long term injury to a key player, the Phillies might make a move to bring in someone better to fill the vacancy.
But then, since DD has been in charge, I have been surprised by some pretty significant moves, so there is always the chance that something unexpected happens this spring.