The Royals have yet to win in the Barclays Premier League this season and sit bottom of the table with just one point. QPR are one point and one place above Reading but McDermott is aware his side are yet to hit their straps.
"We are still not at the level I know we have got to get to and we can get to or where we have been in the past," he said.
"We are all aware of it, the players and the staff, and if we can do that, the results will follow.
"Fundamentally I just think in the last couple of games we haven't done ourselves justice and that is what is galling for me because I know we are better than what we have shown in the last few games."
McDermott is targeting a decent cup run and believes victory over QPR could give his side a lift ahead of their next league assignment against Newcastle at the weekend.
"It is not a distraction it is another game and after the last two games we need to really get our identity back and what we are as a team and that is important to us so that is what we are aiming to do," he said.
Mali international Jimmy Kebe is set to play some part in the match after missing the start of the season due to a hamstring injury.
Experienced striker Jason Roberts is also close to returning to the first-team fold for the first time since the end of the last campaign and McDermott feels his squad has missed the influence of both individuals.
"They are big players for us," he said. "They were very important players for us last season so we need them back and we are looking forward to getting them back."