IT wasn't that long ago that Peter Stringer was seen as the only viable option at scrum-half for Ireland. Then, Tomás O'Leary crashed that one-man party.
At the moment, Munster's Conor Murray is the man in possession of the green jersey, making the vital breakthrough at the Rugby World Cup and further pressing his claims with a Man of the Match impact against Llanelli Scarlets on Sunday.
Then, there are Leinster's perceived home nine Eoin Reddan and their perceived away nine Isaac Boss, locked into an intriguing head-to-head.
This is not entirely true. Boss has started five of the post-World Cup matches, including home dates against Munster and Cardiff Blues in the PRO12 League.
However, the trend does exist for the Heineken Cup in which Boss has been selected away to Montpellier and Bath; Reddan at home to Glasgow Warriors and Bath.
How does Boss view the perception that he is the 'old dog for the harder road'? "It probably does look like that. I hope not," he conceded.
"The away matches are a lot tougher, especially when you look at the weekend. It would have been nice to be on for the 70 minutes when the team is playing expansive rugby."
Leinster isn't the only club dealing with a difficulty over who to choose at scrum-half. Ulster coach Brian McLaughlin has to solve a conundrum where expensive import Ruan Pienaar hovers between nine and 10 and Paul Marshall has recently put his hand up for higher honours.
The signing of Pienaar was the signal for New Zealander Boss to travel south for a few seasons: "Hence, that was part of the decision from me to come down. It was the best decision I ever made. I wish I made it earlier," he said.
"He won tremendous games for them last year. He is a world-class player. He is a match winner for them, a great goal-kicker. That makes it very difficult for Marshall."
This is not to say that Boss is convinced of the pecking order at Ulster where Ian Humphreys has held on at 10 for the Heineken Cup with Pienaar moving to nine to the exclusion of Marshall.
"Sometimes I think he deserves more of a crack than he's got lately. If he gets a chance he will definitely be out to prove a point. He has been doing really well of late," added Boss.
"He is a solid passer, strong kicker and a very good runner of the ball. He is involved in everything. Anytime there is a turnover, he is right there where the ball is.
"His energy is amazing around the pitch. He is one of those who can make a 60-70 metre break that could turn a match around."
This 'Boss man' knows better than most at Leinster how the Northerners would love nothing better than to bring the shock factor to The RDS on St Stephen's Day.
"They've been going well lately. They've been happy with their last couple of matches. But, if you switch back to the league, their form there has been a lot different than in Europe," he said.
"They've got a tough two matches (coming up) in a short turnaround. I'm sure they won't want to drop anything. They never lack motivation coming down here.
"Any time you play an Irish province there is always a grudge there. I was part of that (at Ulster) for a few years. I know full well that they are champing at the bit to have a go at us."
Expect fireworks on St Stephen's Day.