It seems as though he is legitimately injured, from the Nix twitter:
When is he due back from injury?
— Dale Warburton (@Dale_Warburton) August 23, 2017
It could be several months at this stage - we're hoping Louis can either get an NZ Prem or an Australian NPL campaign under his belt. Cheers
— Wellington Phoenix (@WgtnPhoenixFC) August 23, 2017