Ulster's defensive linchpin Payne could miss the entire Six Nations with long-term kidney trouble, paving the way for Robbie Henshaw and Ringrose to reprise their burgeoning Leinster centre partnership in the Test arena.

Ireland boss Joe Schmidt has been at pains not to rush Ringrose's development, but Dempsey now believes the hugely-gifted midfielder is ready to thrive on the international stage.

"Garry has barely scratched the surface of what he can do," Dempsey told Press Association Sport of Ringrose.

"He just bounces onto the training field. And we're just constantly looking forward to seeing what's going to come next.

"He just loves playing, training; he loves the game and all that's involved with it. He doesn't see this as a job.

"He loves expressing himself, and certainly we'd never, ever want to curb that in any way because it's so refreshing.

"Hopefully he'll just keep getting better and better as time goes on."

Ireland will open their Six Nations campaign in Scotland on Saturday, without star fly-half Johnny Sexton who has failed to overcome a calf problem.

Flanker Peter O'Mahony will miss out with hamstring trouble too, while wing Andrew Trimble remains a sizeable doubt due to a groin injury.

Ulster's Paddy Jackson should start at fly-half then, with Henshaw and Ringrose likely to pair up for the first time in Test action.

Ringrose remained an unused replacement as Ireland ended their 111-year wait for a win over New Zealand with a 40-29 triumph in Chicago on November 5.

The elusive Leinster centre then claimed his long-awaited first cap a week later as Ireland eased past Canada 52-21 in Dublin.

But it was his showings at inside centre against both New Zealand and Australia at the end of the autumn series that showcased Ringrose's growing defensive qualities.

Head coach Schmidt had been fending off calls to fast-track Ringrose into Ireland's Test side for more than a year ahead of his eventual elevation.

And Leinster backs coach Dempsey believes that extra breathing space has allowed the naturally-gifted attacking centre to develop into a more-than competent defender.

"Defence is far more than just raw power, it's not coming up and smashing guys, it's about reading the game to be in the right position, in terms of footwork, timing and style of tackling," said Dempsey.

"He sees the picture in front of him in terms of defence really well, and there's good connections with guys all around him as well.

"He's developing a good partnership with Robbie (Henshaw) now, that's really coming on well.

"But he's also a very physical defender, he's extremely committed to that part of the game and can certainly offer a punch in the tackle."

While three-cap Ringrose is only just starting his Test adventure, Dempsey revealed the former Blackrock College man has always possessed a natural rugby mind.

"Dealing with him right from the off, even from 17, you could tell he was rugby-smart; he just got it," said Dempsey, who won 82 Ireland caps between 1998 and 2008.

"You could have a real intellectual conversation on rugby with him. He grasped it.

"Even in one-on-one reviews with him he would come prepared.

"He would see the issues, he would highlight aspects for improvement himself.

"He was nit-picking his own game and constantly striving for improvements even at that stage.

"But he's a kid that loves the game and that's his philosophy on it, he just wants to enjoy every moment of it, go out there with a smile on his face, express himself and enjoy the game.

"A lot of kids at that age feel a lot of pressure, they find it hard to deal with it all, but he seems to manage all that extremely well."