It has just been reported, per Gibby's twitter (and mlb.com, because I don't follow Gibby on twitter...yet), that Corbin and Cahill will start the two games in Australia.
Personally, I find this a bit early to make an announcement, although not too early to reach a decision and communicate that to the players. This gives the Dodgers a little bit more time knowing who they will be facing, at least for the majority of the games.
His announcement of this so early makes me wonder where the D-backs are on the rest of the roster. How is it shaping up? I think it's too early to make any definite statements. But here is my take on it so far.
Definitely on the team: Montero, Goldschmidt, Hill, Prado, Trumbo, Pollock, Parra, Chavez, Pennington, Corbin, Cahill, McCarthy, Arroyo, Miley, Putz, Reed, Hernandez, Ziegler, Collmenter, Thatcher.
That's 20 spots. So the following players will be battling it out for five spots on the final roster, and ten spots on the Australia trip: Gosewisch, Blanco, Gregorius, Owings, Tuiasosopo, Campana, Inciarte, Greene, Marte, Delgado, Harris, Mateo, Rowland-Smith.
Obviously (unless a player is acquired) Gosewisch or Blanco is on the 25-man roster, and both may go to Australia. Ditto Gregorius or Owings. Ross has a spot whenever he is healthy, but I don't think he goes to Australia, and may not play until mid-April.
I think Tuiasosopo has the edge on a spot for now, but Campana will have a good shot as well. Delgado, barring a trade, is going to be on the final roster. So I'd take a guess and say that on the 31st, it's those three along with the previous 20 and whoever wins the spring training battles for backup catcher and starting shortstop.