Sheridan labelled his team's display as the 'worst of the season' after substitute Tope Obadeyi came to the rescue to cancel out Ryan Bowman's strike.
Argyle are now unbeaten in five games in all competitions but Sheridan believes his side need to improve if they are to continue the run.
"I've got to be honest with myself for 70 minutes we were very poor and it was probably the worst we have played so far this season. I'm really disappointed with the performance but I thought we could have stolen the points at the end.
"We could have been two or three goals down at half time and I thought we were shocking. Tope (Obadeyi) has come on and got us going in the game and we finished really strong and we managed to get the equaliser.
"I think when we went to 4-4-2 it got us back in the game and in the end helped us get the point. We finished really strong and had two chances late on to win the game.
"I'm happy with a point from the game and now we'll go into our next league game looking to improve on our performance."