  We consider a recent $T$-matrix analysis by Albaladejo {\it et al.}, [Phys.\
Lett.\ B {\bf 755}, 337 (2016)] which accounts for the $J/\psi\pi$ and
$D^\ast\bar{D}$ coupled--channels dynamics, and that successfully describes the
experimental information concerning the recently discovered $Z_c(3900)^\pm$.
Within such scheme, the data can be similarly well described in two different
scenarios, where the $Z_c(3900)$ is either a resonance or a virtual state. To
shed light into the nature of this state, we apply this formalism in a finite
box with the aim of comparing with recent Lattice QCD (LQCD) simulations. We
see that the energy levels obtained for both scenarios agree well with those
obtained in the single-volume LQCD simulation reported in Prelovsek {\it et
al.} [Phys.\ Rev.\ D {\bf 91}, 014504 (2015)], making thus difficult to
disentangle between both possibilities. We also study the volume dependence of
the energy levels obtained with our formalism, and suggest that LQCD
simulations performed at several volumes could help in discerning the actual
nature of the intriguing $Z_c(3900)$ state.
