I'm guessing that Middlesbrough see Coulson as a left back rather than a winger and that Coulson probably sees this as well. I've read that he was a left winger earlier in his career and was pushed back into defence.
Just because a full back looks good when attacking doesn't automatically mean that they would make good wingers. It could be that they are good at running at defences when running from deep. Wingers aren't usually able to do this and sometimes also have to be looking to get behind defences to run onto through balls.
I would hope that this would be a game where Heaton gets a game. If he isn't good enough to face Queens Park then that would be alarming.
Assuming no new signings, I'd go with
Rodgers - McGinn, Heaton, Kpekawa, Coulson - Flynn, McShane, McGinn, Magennis - Smith - Mullen