Even after putting aside the current state of the squad, it seems inconceivable that at any time in the first half of the season McBeth will start most games on the bench. Just as inconceivable playing a back four that the captain or the left sided O'Reilly would be dropped to accommodate Luke.
Maybe we look too much into formation? If McBeth starts in defensive midfield and drops into the back line when defending it's not too much different from him starting in a back three and moving forward when we're attacking (as indeed he's done). Bit like wingbacks who'll make it a back five when called upon.
It's still not ideal as I think McBeth is best when he picks the ball up from the back line and drives forward rather than collecting it further up the park, but needs be. Putting a positive spin on things a centreback pairing of Ashcroft & O'Reilly should be the least of our worries.