Durban - New Zealand-born England recruit Brad Shields had his eligibility queried by former Argentina star Agustin Pichot on Wednesday, and was praised by new team-mate Chris Robshaw.
"Something is missing," tweeted senior World Rugby official Pichot in Spanish, adding in English: "We are losing something, the game is losing something."
Shields qualifies for England because his parents were born there, but the former Argentina scrumhalf is no fan of the rule that allows a player born in one country to play for another.
"When you have players who have not lived in the country they represent, it is not great," the Argentine said previously.
Shields is leaving Super Rugby outfit the Hurricanes after the 2018 season to join London-based English Premiership club Wasps.
Speaking in Durban, where England are based ahead of the first Test against South Africa in Johannesburg Saturday, Robshaw hailed the flanker's hunger "to learn".
"We have got to know Brad only in the past few days, but he is hungry to learn," said the former England skipper and fellow flanker.
"That is what you want from every member of the England squad - hunger and excitement to be involved.
"Brad has brought something new and is trying to soak it all in, be it lineouts, scrums or whatever."
Robshaw skippered the last England team to tour South Africa in 2012 and they lost the series 2-0 with the dead-rubber third Test drawn.
That was the fifth attempt by Englad to defeat the Springboks in a series in the republic and all have failed.
England coach Eddie Jones, an assistant coach of the South African 2007 Rugby World Cup-winning team, will name his first Test side Thursday.
Whoever he chooses, there will be multiple changes from the last match, a 24-15 Six Nations loss at home to Ireland, with only eight of the Twickenham starters travelling to South Africa.
Among the absentees is injured hooker and captain Dylan Hartley, whose role as skipper has been taken by flyhalf Owen Farrell.
After Johannesburg, South Africa and England play in Bloemfontein on June 16 and in Cape Town on June 23.