The Latics, who are bottom of the table, suffered another defeat on Monday at the hands of Manchester City and are now without a win in seven.
However a win over QPR could lift Wigan out of the relegation zone and McCarthy feels they can take confidence from the City game into this weekend.
He told Wigan Today: "We finished the game strongly, but we just couldn't find that final ball to test the keeper and score an equaliser.
"We had to find a reaction because before the break we weren't ourselves - we were giving the ball away and struggling to find any rhythm.
"Having got ourselves back in the game, it was frustrating not to be able to get some reward in terms of points on the board as well.
"But we were straight back into it at training yesterday, and we need to have a right good go at these final 17 games.
"There's no looking down now, only up - and we'll go into every game confident of getting the points we need with the help of our fans behind us."