The Scots are looking to break an 18-year drought for appearances at the finals of a major tournament.
They currently sit third in Group D, with four qualifying matches remaining. The first two nations in each group secure automatic qualification to the European Championships in France.
"Competition for places across the squad is fierce, but midfield is really tough," McArthur told the Daily Express.
"As well as the guys in the squad, there are a number on the outside who may feel they deserve a chance.
"That means whenever you get a chance to play you feel you have to take it."