Old Glory owner Paul Sheehy says Tendai Mtawarira's decision to head Stateside is a "game-changer" for Major League Rugby.
The Barbarians produced a storming finish in an entertaining encounter at Twickenham, but Fiji held on to lift the Killik Cup.
Winning the Rugby World Cup with South Africa was Tendai Mtawarira's last act for the Springboks, and he called it a "perfect ending".
Makazole Mapimpi, Tendai Mtawarira, Lukhanyo Am and Herschel Jantjies are set to feature for the Barbarians at Twickenham.
South Africa will be aided by the vast experience of Tendai Mtawarira, who will equal a Springboks record, when they take on Argentina.
Rassie Erasmus has made two changes to the South Africa side to face England in what will be a landmark Test for Tendai Mtawarira.