The newly-promoted club were beaten 3-0 by fellow strugglers Sunderland on Tuesday evening to leave the Royals six points from safety with just nine points from 16 games.
And McDermott has urged owner Anton Zingarevich to add to the squad in the transfer window after admitting that the club may have failed to do enough to strengthen.
"The club made a decision in the summer - we didn't invest in the summer," said McDermott.
"We all know that January is a difficult window. We are fighting a battle here.
"That will be down to the owner to see where we are at. I believe we need to do that.
"We are in such a stronger position financially, whatever the outcome of this season is, than we were two years ago, a year ago.
"We want to get out of this, so we have to do everything we can in our power to get out of it, and if that includes January, my view is that we have to do what we have got to do."
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