PFF does a good breakdown of Tana in 2010 just adds some persepctive to the discussion Moss played 40% of his snaps from the slot:
2010 Snap Breakdown - Santana Moss | ProFootballFocus.com
For base personelle I could definetely see Moss at X and Garcon at Z.
Like GT said Moss did play a lot of X in base last year and under Zorn Moss was the X.
If Garcon is the the No.1 option and featured Z receiver and there is an open competition at the X I put my money on Tana.