Flannery is a member of a large technical team along with New Zealander Tony Brown and analyst Felix Jones, who are plotting the Springboks challenge for a third successive Rugby World Cup in 2027.
He says it will not be easy to dislodge the world number one side, not just because of the ability of the players, but also the way the team is run.
“Rassie is a genius, an incredible coach,” Flannery told RTE. “He’s built something very special. I’m not sure we’ll ever see anything like it again.
“He empowers people, he brings the best out of everyone, and he’s incredibly kind. When the top guy makes all the coaches feel valued and heard, that creates an environment for success.
“Having a tight coaching group is one of the most important foundations for success.”
Flannery, whose primary focus is defence, helped the Springboks defeat his native Ireland 24-13 in Dublin last month. He admits to taking some flack for working with one of Ireland’s major rivals.
“It is a professional sport and everybody is so competitive. I have been called a traitor a couple of times at the Aviva,” he said.
He also says Ireland will be a contender for the World Cup in two years’ time.
“We have been a little bit spoiled in Ireland for a while,” he said. “People are now starting to panic a little bit. Ireland has a fantastic coaching group and are a really tight group.
“There are lots of good, young players coming through who can put their hand up. There is massive quality there.”