By STEFFAN THOMAS

WAYNE PIVAC has challenged 21-year-old Sam Costelow to prove he is the long-term successor to Dan Biggar after naming the uncapped Scarlet in his autumn squad. Test centurion Biggar has dominated the No 10 jersey since Pivac has been at the helm, with the Wales captain one of the leading outside-halves in the northern hemisphere. With Gareth Anscombe finally back to somewhere near his best since returning from a severe knee injury both he and Biggar look nailed on for next year’s Rugby World Cup. But who backs up the experienced pair is far from certain w...