  The Nelson-Barr (NB) mechanism to solve the strong CP problem assumes CP
conservation, arranges vanishing $\bar{\theta}$ at tree-level and requires
vector-like quarks (VLQs) to transmit the CP breaking to the SM. We analyze the
flavor constraints coming from the presence of one such down type VLQ of NB
type by performing a global fit on the relevant flavor observables. A
comparison is made to the case of one generic VLQ. We find that the allowed
parameter space for the VLQ Yukawa couplings and the mixing to the SM are
confined to a region much smaller than in the generic case, making the NB case
falsifiable in principle.
