I think Cahill's been quality so far this season, Zouma has also looked quality when he's been needed. Great for a third choice, but I agree, we could do with buying another, so that we have 4 world class players to cover the two positions - especially with Terry coming towards the end, he will struggle to play at this level in every game (3 games a week) someone like Varane would be perfect as he's young and won't be demanding to start every week, although not sure if he specifically would join