  Single top quark production at the Fermilab Tevatron Run II (a p \bar{p}
collider with \sqrt{S} = 2 TeV) proceeds dominantly via two sub-processes, a
t-channel W-gluon fusion process, and an s-channel W^* process. We show that
these two sub-processes have different sensitivities to new physics effects in
the top quark's electro-weak interactions. The W^* process is sensitive to new
heavy charged resonances, such as a W' boson, while the W-gluon fusion process
is more sensitive to modifications to the top's interaction, including
flavor-changing neutral currents involving the top quark. We examine the
implications of these results on our ability to measure V_{tb} with confidence,
and propose a quantity R = \sigma_{Wg} / \sigma_{W^*}, which may be studied in
order to characterize the confidence one may place upon a given measurement of
V_{tb} from single top production.
