  Quasiclassical theory predicts an existence of a sharp energy gap E_g \sim
D/L^2 in the excitation spectrum of a long diffusive superconductor--normal
metal--superconductor (SNS) junction. We show that mesoscopic fluctuations
remove the sharp edge of the spectrum, leading to a nonzero DoS for all
energies. Physically, this effect originates from the quasi-localized states in
the normal metal. Technically, we use an extension of Efetov's supermatrix
sigma-model for mixed NS systems. We demonstrate the equivalence of the
supersymmetric saddle-point solution to the standard quasiclassical Usadel
solution, and show that the instanton solution with broken supersymmetry
provides a non-zero DoS at energies E < E_g.
