Michael Brown and Danny Pugh were both recalled for the impressive league win at Charlton earlier this month.
Brown made his first start of the season at The Valley whilst Pugh made his first appearance for a year.
And McDermott insists that Brown and Pugh have shown that the door is never shut to his first team.
"I am not just saying it to pay lip service, but we believe everybody here is very important and no-one is out of the reckoning," he said.
"The fact that Browny and Pughy came in and did so well at Charlton is a great example of that. They were both terrific.
"I see these guys day in and day out and see what they can do in terms of the training they do with Nigel (Gibbs). What they have done is top-drawer and they really are top, top professionals and they have shown that.
"You need that camaraderie between everybody and you want the substitutes to be wanting the lads to do well on the pitch and the ones who are not in the squad to as well.
"In that way, everybody benefits and I don't know any other way of doing things, to be honest."