For months Wallabies observers scratched their heads over why loosehead prop Benn Robinson had missed out on selection, until his recall to the squad for the two-Test tour to South Africa and Argentina.

However, as the Wallabies trained in Sydney over the weekend in preparation for Saturday's Test against the Springboks in Cape Town, head coach Ewen McKenzie - who all along maintained that Robinson was not out of the selection frame - was able to reveal specifics behind what many saw as a perplexing selection snub.

Perplexing: returning prop Benn Robinson's Wallabies omission shocked many. Credit:AFP

McKenzie said the main reason for Robinson being omitted from the domestic three-Test series against France and the Wallabies' Rugby Championship campaign was because he did not grasp the new scrum laws fast enough. "In the scrum area with the transition of laws over the last 12 months, some people have reacted in different ways. He has taken a bit long to adjust," McKenzie said.

McKenzie then credited the Western Force front row from which hooker Nathan Charles and prop Pek Cowan were early selections for the French series and the Rugby Championship. "Consistency of the Force front row … they have benefited from that in terms of selection."