What this means:
Cahill - probably means he'll be at the club either to the end of his career, or until he can no longer hold down a first team spot when in his thirties. Fantastic - he will be an all-time club legend.
Arteta - likely means we'll get to keep him for a couple of years, and then if / when he wants to move back to Spain, there'll be enough time left on his contract to ensure we cash in big time. I mean I hope he also stays lomg term, but realistically he will probably return to Spain at some point - perhaps after the RS finally realize his mate Xabi Alonso is really, really [Poor language removed].
