I'm not defending Coates because he, like several others was woeful today - however I think this was for several reasons:
1) the defence was left very exposed in the first 60 minutes by a 2 lightweight man midfield - noone like a lucas hounding the opposition of giving options to for the ball to be passed out. I think against a strong physical team, this was a tactical error by Rodgers.
2) Jones was looking very shaky from the start, and I suspect not filling the defenders with confidence and so they dropped back to goal whereas Reina would have been shouting for them to push up the field.
3) Coates, as others have said is very rusty and whilst tall he is not muscly enough yet. For uraguay in the copa America he looked great because he is good with his feet and towers over generally smaller opposition, so wins most balls in the air easily. In the uk he doesn't have this advantage and is currently too lightweight.
Yesterdat i believe a combination of being physically weakand rusty led I believe to a poor display. I still think he is technically gifted, and given experience in loan and help to toughen up, he could still be a great defender.