When I look at our squad the defense is weaker than the attack, but the attack falls apart if an injury happens. The defense seems to cope with a ok if a player is injured. I'd priorities attack.
Priority for me is the spine of the team and that is a DM, CM and ST. A top class DM will provide protection for the defence, and will allow the CM's to attack with more freedom. A CM who can drive the team forward and carry the ball. ST for obvious reasons.
