Axle Breather

I have quite a major leak from the Pinion seal on my rear Axle,

The breather on this axle seems quite brittle and old would this cause the afore mentioned leak? or could the bearing need replacement? just wondering as I am ordering parts and dont want to have to do it again because I missed an obvious cause It could be that the seal is worn admittedly just thought I'd pick the well informed brains in the Loonyzone before I decided for sure!

if your going to do one brg you mays well do both not so good to do one taper brg ,more likely seal and flange

OK cheers matey