World champions South Africa tackle the Barbarians in a non-cap exhibition match on Saturday to kick off what head coach Rassie Erasmus says will be a "really tough season".

O'Mahony forms a vastly experienced back row with two former All Blacks, fellow flanker Sam Cane and number 8 Shannon Frizell, who both play in Japan.

Piastri continued to finish fourth while Norris was forced to retire.