Thomas “The Tank” du Toit says Springbok coach Rassie Erasmus will gain some valuable insight when he shares the coaches’ box with Siya Kolisi in Santiago del Estero in Argentina tomorrow night (11pm kick-off, SA time).Kolisi is being rested from playing duties for the big Rugby Championship match against Argentina, and Erasmus has told the media that he wants the loose forward to follow in the footsteps of Duane Vermeulen and become versed in how things go down among the coaches during a match.Vermeulen has successfully transitioned from player to coach by following this path, but…