Andrew Trimble has failed to beat his groin problem so Keith Earls will start on the wing in Ireland's RBS 6 Nations opener in Scotland.

Munster hooker Niall Scannell could make his Test debut after winning the fight with Leinster's James Tracy to understudy captain Rory Best at Murrayfield.

Scannell's Munster team-mate John Ryan also takes a seat on the bench, having been preferred to Connacht's Finlay Bealham as the replacement tighthead prop.

Ryan has just one cap to his name but has impressed consistently this term amid Munster's resurgence.

Paddy Jackson replaces calf injury victim Johnny Sexton at fly-half as expected, with Iain Henderson partnering Devin Toner in the second row.

Sean O'Brien has shaken off his own calf issue to start at openside flanker, with Josh Van Der Flier taking a seat on the bench.

Head coach Joe Schmidt has also drafted Tommy Bowe back onto the bench, with the Ulster wing poised for his first Test appearance since Ireland's 40-23 World Cup quarter-final defeat to Argentina on October 18, 2015.

Ian Keatley will cover fly-half from the bench despite not featuring for Ireland since the Six Nations win over Italy in Rome on February 7, 2015.

Hugely-gifted Leinster centre Garry Ringrose will make his first Six Nations start, while captain Best will make his 51st consecutive appearance in the competition.

Ireland boss Schmidt revealed Munster lock Donnacha Ryan was not quite fully fit to contest selection after suffering a minor knee injury.

"Donnacha had a niggly medial ligament so he didn't train last week," said Schmidt.

Donnacha Ryan is named among the replacements (Getty)

"Tuesday was the first time he trained. He's been super for us in recent times but it's a really tough turnaround.

"We just had uncertainty around him. He trained really well today but we wanted a bit more certainty than that.

"At the same time Iain Henderson has done well for us and Devin Toner obviously too."

Schmidt also admitted linchpin fly-half Johnny Sexton remains a long shot to be fit to face Italy in Rome on Saturday week.

Peter O'Mahony is not expected to beat his knee problem for the Azzurri clash either, though Trimble could yet be back for the Italy trip.

Schmidt insisted Ireland have no fears over Sexton's durability despite a string of injuries this season.

"Johnny Sexton is an outside chance, but Peter O'Mahony is highly unlikely for Italy," said Schmidt.

Jonny Sexton has been hampered by injuries of late (Getty)

"Pete is bordering on grade one grade two with his hamstring. It's not bad but if you push it back too quickly it's a problem.

"Andrew Trimble we'd be pretty confident he'd be alright. His is a niggle, but it would have been a fine line for this week. And we wouldn't want someone starting and going off inside the first 20 minutes.

"There's no one more frustrated than Johnny himself. He was incredibly motivated for this championships. For us he's probably played 82 minutes in the last eight Test matches, so for us it's a real frustration. But we're still hopeful he can come back in and do that for us, but at the same time Paddy has done really well.

"Paddy Jackson played all three Tests against South Africa, played against Australia, and it's not like he hasn't had good experience."

Asked if Sexton's injuries raise fears over his long-term durability, Schmidt continued: "Not really. I don't think there's many players that don't go through a period of injury and a little bit of bad luck.

"It was a very minor injury going into the Castres match and it just triggered an extension of that injury.

"It's just for us getting him 100 per cent fit before we get him back out there."

Ireland team to face Scotland:

Kearney; Earls; Ringrose, Henshaw; Zebo; Jackson, Murray; McGrath, Best, Furlong; Henderson, Toner; Stander, O’Brien, Heaslip.