McDermott's side have won only three of their last nine games in the Sky Bet Championship but lie 10th, six points off a play-off place, in the table following last weekend's 3-2 defeat at Huddersfield.
"We're very much at the stage where we're up and down with the team that we've got," McDermott said.
"We need to be more ruthless in what we do. We get back to 2-2 (on Saturday) and we go gung-ho trying to win the game.
"We didn't need to win the game in the next five minutes, we just needed to do what we had to do to get a result and this is especially so away from home.
"It's something we're working on because I believe we're going to be close.
"If we can get a run of consistency going, we've got decent players, we've just got to learn how to win and what's required to win games, away from home especially.
"Let's see where we are at the end of December. We want to try and be right in the mix, six points off the play-offs.
"I've been here before. If we can get close to where we need to be with 20 games to go, who knows what could happen?"
Meanwhile, McDermott said his side's poor away form is cranking up the pressure on them to gain maximum points from their home matches.
The Whites have lost their last five Sky Bet Championship games away from Elland Road and have won only twice on their travels this season.
"I think what's happening with us, because of what's been happening away from home, it puts extra pressure on you to win at home," said McDermott.
"You have to try and win that game. If we win the game (against Yeovil) on Saturday then we're looking at the top nine, top eight and then we go to Charlton.
"So if we can win this one we obviously get the feelgood factor back and then the aim is to win three or four games on the spin, which is what we haven't been able to do just yet.
"Playing at home the last game we played very well. We've won the last couple at home. We've got to do all we can to win on Saturday and then we'll look at the Charlton game."