John Fay reported that there were 16 position players and 9 pitchers in Pittsburgh. Henry Rodriguez, among others, did not make the trip. That kinda narrows it down.
With the roster about to drop in about 5 minutes, here's my prediction:
Catchers (3): Hanigan, Mesoraco, Miller
Infielders (6): Votto, Phillips, Frazier, Cozart, Hannahan, Izturis
Outfielders (7): Choo, Bruce, Ludwick, Heisey, Paul, Hamilton, Robinson
Relievers (8): Chapman, LeCure, Marshall, Hoover, Parra, Simon, Duke, Leake