  We analyze $K\to \pi \nu\bar \nu$ rates in a model with a TeV-scale
leptoquark addressing $B$-meson anomalies, based on the flavor non-universal
4321 gauge group featuring third-generation quark-lepton unification. We show
that, together with the tight bounds imposed by $\Delta F = 2$ amplitudes, the
present measurement of $\mathcal{B}(K^+ \to \pi^+ \nu \bar\nu)$ already
provides a non-trivial constraint on the model parameter space. In the minimal
version of the model, the deviations from the Standard Model in
$\mathcal{B}(K^+ \to \pi^+ \nu \bar\nu)$ are predicted to be in close
correlation with non-standard effects in the Lepton Flavor Universality ratios
$R_D$ and $R_{D^*}$. With the help of future data, these correlations can
provide a decisive test of the model.
