In a statement late on Friday, the players complained of the "obsolete infrastructure" at both the Estadio de Vallecas and at the club's training grounds, which they said they had been unable to use for months in pre-season.
On Saturday, LaLiga announced that the Oviedo match could not proceed because of the poor pitch, adding that heavy rainfall had thwarted efforts to restore turf that had recently been replaced.
Rayo's players painted a picture of systematic neglect, complaining of "deficient conditions, worsening as the season progressed" at their home ground, along with "a lack of hot water in the showers on certain days" and inadequate cleaning.
They said they had repeatedly raised their concerns with club president Raul Martin Presa, but to little effect.
Rayo Vallecano did not immediately respond to a request for comment.
Oviedo issued a statement sympathising with the Rayo Vallecano squad, but complaining that the postponement of the match just four hours before kick-off would cause them "clear damage".
Rayo are due to host local rivals Atletico Madrid next weekend.