There is more of a squeeze than you think. Both Moller and Ballard need to be upgraded or dropped. I would expect Moller to stay, Ballard is harder to tell. At the moment only Sylvia is the only "out" player. We will need to delist (retire) or trade 3 to 4 additional players IMHO.
The draft this year is very shallow. We should not be going deeper than our third pick (required minimum) other than to top up our rookie list. Plus any we trade in but that could involve players rather than picks.
I reckon we have plenty of space on our list to maintain someone with the proven potential of Mora if he has a chance of getting over his soreness in the knee. Also I think it makes more sense to give Mora another 1 year contract extension than draft a low potential youngster from late in this draft - better to tide it over for another year and if Mora does not come up next year then next years draft is much deeper.
Realistically, I would have the following players being delisted before Mora and we only need 4 at most assuming we want to upgrade Moller:
Sylvia (gone already)
Crowley (our depth and the game has gone past him)
Duffy (maybe re-rookie, no other club will take him)
McPharlin (lets face it, he was convinced to go another year but he will probably retire this year)
Hannath (not sure we are best served by having him as well as the others including Moller on the list, Apeness has more potential as a genuine forward/ruck and you could use the spot to grab another ruck/KPP prospect)
Duffield (depth player now and age is against him, clearly RTB prefers Sutty, Sherro etc. in his role now and other youngsters pushing up as well).
I am pretty sure Mora is training now with the intention that if his knee shows signs of improvement they will give another chance come the end of the year.
Ballard is very borderline and a rookie anyway - his problem is disposal and that is a hard thing to fix up but critical in the present game against teams like Hawthorn.