In the recently-aired BBC documentary charting the story of Ireland's number 10 jersey, Ronan O'Gara offered an insight into his relationship with David Humphreys.

O'Gara made the point that even his relatively harmonious contest with Ulsterman Humphreys needs to be placed in the context of international sport.

"It got heated at times," recalls the 44-year-old, who won 128 caps between 2000 and 2013.

"He wasn't going to go silently. He was never going to give you the jersey. Everyone thinks he's a gentleman. He is a gentleman but there's a ruthless side to him because if there wasn't, he wouldn't be the competitor he is."

Head coach Andy Farrell arrives at this year's Six Nations with the fabled 'good headache' in regards to selection options. With the exception of James Lowe, the squad that performed so well in November are fit.

In the intervening period, the four provinces have all booked their place in the last-16 of the Champions Cup, while many of Ireland's outstanding autumn performers have played little rugby.

The stars of the Irish show in December and January have largely been those who didn't feature in the autumn. James Hume, Gavin Coombes, Michael Lowry and Jack Carty are among those to have been rewarded for excellent form with a place in the Six Nations squad, but are now facing an uphill task in terms of breaking into an Ireland starting line-up that is itself flying high.

With Farrell due to announce his team for Saturday's opener against Wales on Thursday, it's unlikely he will stray far from the settled side that performed so well against Japan, New Zealand and Argentina.

If that is the case, it begs the question of how the in-form club players approach the challenge of breaking a seemingly established pecking order. And how do the relationships between players battling for the same spot in an ultra-competitive environment manifest themselves?

"Sport is about patience," says Humphreys, who played 72 times for Ireland between 1996 and 2006.

"Some people will look with a great degree of envy at their peers and other players that they don't feel are as good as them getting an opportunity. But if you hang around, work hard and play well then you will get an opportunity.

"Then the challenge is once you get that opportunity, are you in a good enough place to take it?"

'Hume must avoid frustration amid intense centre competition'

The challenge facing Hume is particularly fascinating. The 22-year-old was in camp for the entire autumn series but did not feature in any of the matchday squads. Before leaving, he sat down with Farrell to discuss how he could further his selection case.

The Ireland boss told Hume the next block of games, which included a number of inter-provincial derbies and four Champions Cup ties - were crucial in proving he had the ability to consistently perform at the highest level.

The Ulster back delivered - and was arguably his side's standout performer - as they won all four European games and beat Leinster away for the first time since 2013.

Now back in Ireland camp he still faces a challenge if he is to see the field during the Six Nations as he competes for a jersey with three of Europe's elite centres in Robbie Henshaw, Bundee Aki and Garry Ringrose.

"He's going into a position where there are two Lions - and arguably there should be three - and the message to him should be that he will at some stage become a regular in that Irish team," Humphreys adds.

"Every time he goes down and trains with Ireland he is benchmarking himself against some of the best players in the world in his position. If he comes away from every session and every week having competed, then when his chance comes, he will be better prepared for the challenge of international rugby.

"I'm really interested to see how James gets on over the next few weeks and if he does get an opportunity, but if he doesn't, he can't become frustrated because he's in a position where there's unbelievable depth of quality."

Sexton's changed approach

For Sexton, his approach to positional rivalries has - through a mix of experience, responsibility and circumstance - shifted considerably.

At 36, he is no longer the feisty young upstart refusing to back down from any challenge presented to him by the decorated veteran O'Gara.

Now he has a captain's responsibility to nurture every other player in the squad - even those who, in an ideal world, would look to replace Sexton as the starting fly-half.

"As a leader of the team you need to make sure you're working with guys as well. It's that balance across the team really. Joey [Carbery] and Jack [Carty] are great lads, we work together most of the week and that's how it will stay.

"I think I've changed a lot over the years, making sure you're working with people as opposed to constantly trying to motivate. I try not to be over-bearing on the other younger fly-halves because they'll learn more if I set the right example and show them my standards day in, day out.

"I'd like to think you show them enough that if they ever want to ask questions that I'm not going to ignore them.

"They're pretty mature, good players and are vying for that number 10 jersey as well, so they probably don't want to give too much away either."

With Sexton's starting spot assured, Carty and Carbery are fighting for a place on the bench and a chance to influence the game in the championship minutes.

An inevitable frustration - and desire to take one's role in the team - to that of a nailed-on starter exists in every player. But the role of the replacements continues to grow in its importance - numbers 16-23 are no longer bit-part players, but finishers.

Ireland are enjoying an eight-game winning run and the mood music surrounding the team has totally transformed from what it was 12 months ago. Is that wider picture something the players in the camp ought to be mindful of?

"In terms of the team being successful, while I wanted to play I also knew that team selection was about getting the best team on the pitch," reflects Humphreys, 50.

"There's nothing better in sport than being part of a successful team. It makes everything so much more enjoyable."