Does it matter if I play a player out of position?
The answer to that is a mix of both yes and no. In an ideal world, with all things equal, you’d have a player Accomplished or better in each position. They’ll be more comfortable, they’ll perform to a higher and a more consistent standard and will be less likely to be targeted as a weakness by the opposition.
This isn’t to say that you can’t play someone out of position though, either on a regular basis or in times of need. For the latter, you can often plug someone in to ‘do a job’ and they’ll typically perform well enough to get by, particularly if the rest of the team is strong and the tactical structure helps to support them. Playing someone out of position longer-term, on the other hand, can work if the player’s attributes lend themselves well to the position and role assigned to them, and they’ll gradually learn and improve in that position the more they play there.
This ties into the overall concept of footballing ‘universality’; the idea that any player can play in any position as long as he’s well-trained and has a certain number of fundamental attributes in place. This is much harder to commit to and make work in practice than it is in theory, but the concept of a player being used in an unfamiliar or entirely different position isn’t a new one, and it isn’t something you should necessarily shy away from if you feel it can work within the framework of your tactics.