Ireland have their very own version of the Blue Bulls.
It is a two-man tag team. Jack McGrath and Cian Healy have been locked in competition and partnership for Leinster's Blues for most of Healy's career and all of McGrath's.
It is a local Dublin rivalry, northside versus southside, Belvedere College versus St Mary's College, Clontarf versus St Mary's.
It all began with Healy.
The explosive loose-head made his Leinster debut as 64th minute replacement against the Scottish club Border Reivers in the Magner's League back in May of 2007.
He was just 19 years old and would start 16 of his first 20 caps on the bench, 20 of his first 28.
It all changed in January of 2009 when he embarked on ten straight starts culminating in the glorious Heineken Cup final against Leicester Tigers.
The quick ascent did not quite come in time to squeeze into Ireland's Grand Slam drive at The Millennium Stadium.
Healy broke into the international arena by making his debut against Australia in November later the same year.
He held his ground, and made some, over nine caps that season, seven of them for 80 minutes.
Healy had arrived.
He owned the number one shirt for five seasons, rising to the best in the world, Ireland's forwards coach Gert Smal rating him better than even Tendai 'The Beast' Mtawarira.
The ravage of injury began to take hold, slowing the previously unstoppable power athlete.
From 2013, he was stalled by a serious ankle ligament injury, a torn hamstring and a serious neck injury which threatened to end his career in May of 2015.
Through this dispiriting three-year stretch, McGrath began to make a convincing case as a durable, rock-steady prop who made few mistakes.
Two years younger, his progress was slightly slower, making his Leinster debut as a 20-year-old for 14 minutes against Glasgow Warriors in April 2010.
McGrath spent more time coming off the bench than starting for four seasons, racking up 12 starts and 26 impact involvements.
In the beginning, Healy's consistent injury toll was what opened the door and McGrath took full advantage by staying fit and focused.
A thoroughly well-earned first Ireland cap came against Samoa in November 2013.
After that, he took over the mantle of first choice in his second season for Ireland, starting regularly.
Last season, McGrath held the edge for seven of eight internationals before embarking on the Lions tour to New Zealand.
All the while, Healy was rebuilding his reputation, playing in 12 of Ireland's internationals, although, there was just one start in the Six Nations against Italy. He had to play second fiddle to McGrath for the other five.
Now, the time has come for Joe Schmidt to reveal whether Healy has made it all the way back from near oblivion or whether McGrath remains Ireland's number one.
For the first time, in a long time, the identity of Ireland's number one loose-head is up for grabs.
There are few greater front row tests than South Africa. Of all the selection decisions to be made, this is the most interesting and informative.
Will McGrath hold his ground? Will Healy take back what was once his?
Forwards coach Simon Easterby was quick to add Munster's Dave Kilcoyne to the argument.
"I don't think there's many teams across the world at the moment who have three loose-heads with the destructive ability across the game; defence, attack, scrum, line-out," he said.
"When you look at the three of them, they're not all the best at everything.
"But they're certainly pushing each other to be right up there - in terms of world rugby - in that loose-head position."
It would still come as a surprise to see Kilcoyne split the difference between McGrath and Healy.
"We all know how important the scrum is and how important the loose-head is, in terms of his scrummaging and how destructive they can be as opposed to a tight-head.
"The work around the pitch is invaluable and the three of them across the board have been pretty special this season.
"The test comes on the weekend against one of the most formidable forward packs
"We have to be right on our game to contest and counter."