After three successive wins, the Spireites had given themselves a chance of avoiding the drop and they led 2-1 with 20 minutes left only for Yeovil to hit back.
Sheridan said: "I am very disappointed after the joy of last season. It has been a very poor season.
"It would have been great to give ourselves an opportunity at home next week in the last game [against Brentford].
"You get 2-1 up and the way we were playing we could have taken control of the game. But we were punished for bad defending. In the second half in particular we played well and created a lot of opportunities. We should have scored more goals."