Below are squad players listed by primary position, and also placed in order of preference (my opinion after gazing through Link's crystal ball)
Looseheads:
Benn Robinson (Waratahs)
Scott Sio (Brumbies)
Paddy Ryan (Waratahs)
Hookers:
Stephen Moore (Brumbies)
Tatafu Polota-Nau (Waratahs)
Saia Fainga’a (Reds)
Tighthead Props:
James Slipper (1,3)(Reds)
Ben Alexander (1,3) (Brumbies)
Sekope Kepu (Waratahs)
Locks:
James Horwill (Reds)
Rob Simmons (Reds)
Kane Douglas (Waratahs)
Hugh Pyle (Rebels)
Scott Fardy (Brumbies)
Blindside Flankers / Number 8’s:
Ben Mowen (Brumbies)
Peter Kimlin (4, 5 ,6, 8) (Brumbies)
Hugh McMeniman (Force) (4, 5)
Dave Dennis (Waratahs)
Ben McCalman (Force)
Jake Schatz (Reds),
Openside Flankers:
Liam Gill (Reds)
Michael Hooper (Waratahs)
Halfbacks:
Will Genia (Reds)
Nic White (Brumbies)
Nick Phipps (Rebels)
Flyhalfs: Quade Cooper (Reds)
Matt To'omua (Brumbies)
Bernard Foley (Waratahs) (10, 15)
Inside Centres: Christian Leali’ifano (Brumbies) (10, 12)
Anthony Fainga’a (12,13)(Reds)
Mike Harris (Reds) (10, 15 cover)
Outside Centre: Adam Ashley-Cooper (Waratahs)
Tevita Kuridrani (Brumbies)
Wings: Israel Folau (15)(Waratahs)
James O’Connor (Rebels)(10, 12,15)
Nick Cummins(13) (Force)
Joe Tomane (Brumbies)
Peter Betham (Waratahs)
Chris Feauai-Sautia (11,13,14)(Reds)
Fullback: Jesse Mogg (Brumbies)
As you can see here ,there is really no need for a player like Horne, McKenzie must believe that with Leali’ifano,O’Connor, Fainga’a & Harris they have enough cover for the Inside centre. Regarding 13, Kurindrani & AAC (Adam Ashley-Cooper) are leagues in front of him. He is also a like for like pick with Fainga’a who also is a 12,13.
I’m not fussed over his omission, he would only be used as bench cover so it does make sense to use a player with versatility to cover other backline positions, , i.e. Harris
All in all a pretty well rounded squad, he's showing intent to blood the up and comers, Pyle, Fardy, Toomoa, Foley, Kurindrani, Bentham, Sautia & Shatz, all who look like future wallabies (reservations about Shatz's size & Sautia & Bentham still)