Few players divide opinion in Irish rugby like Jamie Heaslip, but perhaps it is those who have packed down directly against him who know the Leinster No 8 best.
During his time at Ulster, former Springbok Pedrie Wannenburg went toe-to-toe with the Naas native several times, most notably in the 2012 Heineken Cup final which Leinster won well.
That was the South African's final game in white – indeed, both of his last two games came against the Blues, although it was Sean O'Brien who wore No 8 in the league game a month earlier.
Wannenburg has since moved his family to France to link up with Castres where he won the French Top 14 title last season.
On Sunday, he is likely to come face-to-face with the Ireland vice-captain once again – albeit possibly off the bench, where he has been used most this season – as speculation mounts that their on-pitch rendezvous could become frequent once again next season as Heaslip contemplates a move to Toulon.
And the 33-year-old former Bulls star is not surprised that the Lion is attracting so much interest inFrance.
"Heaslip is a really good No 8, he's solid at the back (of the scrum), a hard runner and a clever player," Wannenburg said.
"He was always difficult to play against – I really rate him as a No 8, he has done well for Leinster, for Ireland and he's a tough candidate. He's a different player, he's unique for what he brings to the team and his experience is phenomenal for Leinster and Ireland.
"He's a really good player and any team in France or if he stays in Ireland... he would be a good player for any team."
The move to France has suited Wannenburg in some ways. Like Ulster, Castres have a core of South Africans that act as a support network for newcomers.
As for the rugby, there have been some adjustments for Wannenburg as he moves from the structure employed by Ulster and the Bulls to a more off-the-cuff game in France.
"It's more structured in Ireland, you know what you are doing in the next four or five phases over there, but here it's one off and after that ... then it's the flair of the players. That's the way it is, that's the way they play it and you can't change it," he said.
"It's why very few southern hemisphere coaches make it over here. The guys that are coaching in South Africa, or Ulster as well, they don't like their structure, they play off the cuff, basically.
"It's something you have to adapt to after playing with structure for so many years, but it's nice in a way that you can go and play."