“The red card is a big impact on the game and then of course they score a goal from the penalty which is a double blow,” said the 25-year-old.
“It was a disappointing game despite us playing very good football for spells but, we’ve got a massive match against QPR at the weekend and that has to be the main focus from now on.
“It is the biggest game of the season now in terms of trying to show people how we can battle against adversity like we did last season.
“We need to draw a line in the sand now because we’ve played with 10 men for 80 minutes and that is never a regular occurrence in football but, us controlling the ball and passing well is regular in our games so that is what we have to focus on.”
McArthur praised the use of the squad as a whole over recent games and says it is that strength in quality that can continue to provide results.
“We need to work hard to get all three points and really push up the table.
“We’ve got a good enough squad to deal with suspensions and injuries, and moments like these are dealt with because of the benefit of having a strong squad.
“It is up to us as players to take chances with both hands and work to stay in the team and do whatever it takes to win football games.”
The Scottish international midfielder reserved particular praise for the way in which Adrian Lopez has stepped into the team in recent games.
“Adrian has been playing really well and he has shown tremendous quality to come into the team having not been a regular starter, yet he still performs to a very high standard.
“I thought he was fantastic last week against Manchester City and he did it again last night, coming on at half time for Gary (Caldwell).
“Adrian has played a big role in the team recently and he will want to continue that, as will everyone in the squad.”