I'm considering trading Houston in mainly because I have to fix my defence, as it has too many Rookies (I will have to miss out on B Smith, hmmm). I'm leaning to D/M Houston because I can put D/M Rivers in the midfield, might be handy later through the Byes and I don't have any PTA players, again balancing my team to help it during the Byes.
As mentioned, yes he may go back to defence, but who knows? Houston trained preseason with the midfield, so I expect him to play mainly midfield.