  The complete absence of isolated quarks reaching particle detectors after
high energy collisions suggests that some physical mechanism generates
resistance to their propagation in the vacuum. In order to reveal such a
mechanism, we analyze the fate of an infinitely heavy quark that is initially
propagating in the vacuum with inertial motion. The non-perturbative structure
of the vacuum is treated here using the gauge/ gravity correspondence, the
isolated quark on the boundary gauge theory is dual to a trailing string moving
in the bulk of a higher dimensional curved space. We find that, for a large
class of non-conformal gauge theories with a holographic dual, the geometrical
structure of the bulk geometry induces a drag force on the quark that moves in
the vacuum. In addition, we show that for these gauge theories there will be
the presence of such a drag force due to its vacuum whenever the dual bulk
geometry generates a linear potential for a $q\bar{q}$ pair. The relation of
the linear $q\bar{q}$ potential with the drag force on the isolated quark is a
holographic piece of evidence that both phenomena are different manifestations
of the confinement of quarks.
