Although M. Austin is quite attractive for Week 1, I would honestly go with Moreno for Flex this week! Be wary that Moreno will most likely lose GOAL-LINE touches, which rack up a significant amount of fantasy points for most leagues.
10 team H2H league, standard scoring [NFL.com]
QB: A. Rogers
RB: MJD, S. Jax, J. Starks, D. Murray, M. Bush
WR: M. Wallace, B. Marshall, P. Harvin, M. Colston, L. Robinson
TE: O. Daniels, J. Gresham
K: Sebastian Janikowski