I think being the last man is just part and parcel of the work of a defender, particuarly a centre back. It's something everyone needs to deal with because there's no fail safe way to defend, there will always be times where they need to be desperate to be effective. I'm sure Kos isn't helped by the fact our defending as a team is so poor but it's difficult to ignore him as an individual when these moments keep happening to the same person.
Vermaelen has a good action-man sidekick.