Former Ireland number eight Jamie Heaslip believes Caelan Doris is the form backrow in the country at the minute and is fully capable of making the step-up to international rugby. 

The 21-year old Leinster player will make his Ireland debut at the weekend as the Andy Farrell era begins against Scotland in Dublin.

Doris is one five changes to the Ireland starting XV since their last outing, that grim loss to New Zealand in the Rugby World Cup quarter-final in October, the result which brought a crushing end to Joe Schmidt's often glorious reign in charge of the national team. 

Jordan Larmour replaces the venerable Rob Kearney - who started every game of each of Ireland's four victorious Six Nations campaigns since 2009 - at full-back, Andrew Conway dislodges his Munster team-mate Keith Earls, who wasn't able to train fully this week, on the wing, Rob Herring takes the place of the retired Rory Best, and Doris is selected instead of Peter O'Mahony, who drops to the bench. 

In the only other change, Bundee Aki, suspended for the infamous quarter-final following his red card against Samoa in the last pool game, is swapped in for Robbie Henshaw at inside centre. 

Ireland head coach Andy Farrell speaking to the media at the team training camp in Portugal on Monday

Doris, who was born in Ballina but educated at Blackrock College, has caught the eye as Leinster have largely glided through the 2019-20 competition, still unbeaten in both domestic and European competition. 

"I don't think it's a big step," says Heaslip. "He is more than capable of playing international rugby. In a metaphorical sense, yes, club rugby to international rugby [is a big step].

"For the standard and level that he is playing at and capable of, I think he will take it in his stride. 

"I think he's the best number eight in Ireland right now. He's probably the form backrow in Ireland right now. 

"I think he has a great ability to play both sides of the ball well. Attack and defence. It's his mindset and his grunt and his relentless nature and his consistency is what's getting him the starting spot this weekend."

Heaslip introduces a slight caveat in the shape of Leinster's ultra serene progress this season, noting that the margin for error may be a bit tighter in an Ireland side which is competing in a different arena and at a different stage of its development.  

 "It's international footy now. So, the room for error is that bit smaller than European rugby. 

"You could argue that no one's challenged Leinster so the room for error that he's become used to this season - compared to what is coming down the line in international rugby - is bigger.

"He's got to react to that. But you don't know until you give the kid a go. It's great to see he's got the nod. I think he has the potential to be around for a very long time."

Doris arrives into a back-row unit which, after years of being feted as one of Ireland's primary strengths, shipped a mountain of criticism throughout a difficult 2019. 

Following the annus mirabilis of 2018, Ireland proceeded to lose five of their 13 games across the most important ten months of 'the four-year cycle', with many of the victories themselves arriving after underwhelming displays against mis-firing or lowly opposition. 

For Heaslip, an international back row for over a decade, the nature of the position is changing and becoming more demanding, requiring a more all-around game and a greater range of skills. 

"The game is getting faster. The percentage of high speed running is changing in the game and the ball is in play longer nowadays. 

"You need players that are able to go the distance and play at speed, take the contacts and get back up and go again. You need players that are multi-faceted as well.

"The days of a guy being good on one side of the ball, and good at only doing one thing on one side of the ball, there's not a whole lot of time left for those players.

Caelan Doris makes his debut on Saturday against Scotland

"That's where some players are potentially feeling the pressure come on because you have a crop of players coming through who can do many things.

"That means you've go to do that one thing unbelievably well because there's someone who can do that and other [things]. It's a good headache for coaches." 

Rory Best's long goodbye finally concluded late last year and the veteran Ulster hooker left a vacancy in the captain's role. 

That has been filled - to no one's great surprise, and certainly not to Heaslip's - by Johnny Sexton. 

Heaslip doesn't foresee much upheaval in this change, either for the player personally or the team more generally. The 10 position is a critical leadership role and Sexton has always conducted himself much like a captain on the field. 

"Well, he's already the captain at Leinster. At national level, he's pretty much been the captain for the last two years, in my book.

"Any team that I've been on with Johnny, even if he's not captain, he'll still let his point of view be known.

"He has to do because he's in the driving seat. As a 10, he's the quarterback, he's directing the team, he's the one on the field calling the plays, essentially.

"He's the one trying to read the game and move the ball around, read the opposition. Other players will be feeding into it but he's the one in the driving seat.

"I think it's a really good evolution step for him as a player. I think he's at that right age and stage of experience in the game and life experience to be the main man, be the captain, be the leader."

Follow Ireland v Scotland (kick-off 4.45pm) on Saturday via our live blog on RTE.ie/Sport and the News Now app or listen live on RTÉ Radio 1's Saturday Sport. Highlights on Against the Head, Monday at 8pm on RTÉ2 and RTÉ Player. 

Jamie Heaslip was speaking at the launch of the Aviva Sensory Hub, Aviva's latest initiative to make Aviva Stadium a more inclusive space. For more information  follow Aviva on Instagram, Twitter, and Facebook using #SafeToDream or visit www.aviva.ie/sensoryhub