  We analyze the validity of BCFW recursion relations for currents of n - 2
gluons and two massive quarks, where one of the quarks is off shell and the
remaining particles are on shell. These currents are gauge-dependent and can be
used as ingredients in the unitarity-based approach to computing one-loop
amplitudes. The validity of BCFW recursion relations is well known to depend on
the so-called boundary behavior of the currents as the momentum shift parameter
goes to infinity. With off-shell currents, a new potential problem arises,
namely unphysical poles that depend on the choice of gauge. We identify
conditions under which boundary terms are absent and unphysical poles are
avoided, so that there is a natural recursion relation. In particular, we are
able to choose a gauge in which we construct a valid shift for currents with at
least n - 3 gluons of the same helicity. We derive an analytic formula in the
case where all gluons have the same helicity. As by-products, we prove the
vanishing boundary behavior of general off-shell objects in Feynman gauge, and
we find a compact generalization of Berends-Giele gluon currents with a generic
reference spinor.
