how did you manage to draw up that conclusion. For me both right now, Bartra with his pre-season form and Verm with his general form, are equally bad. Maybe try him at LB where he wouldn't have to mark people. I dreaded everytime an attack came from the left wing with Adriano and Verm there, Atletic players might as well have walked into the box.
That's because the rest of the defence and midfield was crap. Put Vermaelen as a rotation for masch with the rest of the defence and midfield at 100%, and he will do well. But he is not good enough to play with other backups, that is a disaster.
Let's also give him a shot at left back but with alves, pique and masch still there and see how he does. You never know, he could be a decent backup lb.