  We propose a strategy to non-perturbatively match the Wilson coefficients in
the three- and four-flavor theories, which uses two-point Green's functions of
the corresponding four-quark operators at long distances. The idea is refined
by combining with the spherical averaging technique, which enables us to
convert two-point functions calculated on the lattice into continuous functions
of the distance $|x-y|$ between two operators. We also show the result for an
exploratory calculation of two-point functions of the $\Delta S=1$ operators
$Q_7$ and $Q_8$ that are in the $(8_L,8_R)$ representation of ${\rm
SU(3)}_L\times{\rm SU(3)}_R$ and mix with each other.
