Fast-developing tighthead Moore is expected to win his first cap as a replacement, with experienced campaigners Cian Healy and Mike Ross Ireland's starting props.

Ulster hooker Best will win his 71st cap, with Sean Cronin among the replacements and McGrath in line for just his fourth international outing if he joins the fray.

Best admitted Ireland's forwards have sunk their teeth into some testing scrum tussles in training at their Carton House base in Six Nations preparations.

"When we're training in the scrum now, if you don't get it right you're going to get done, which is exactly what it will be like on Sunday," said 31-year-old Best.

"And that's important. It obviously brings competition for places, which is good for everyone, with these young guys coming through.

"There's some real competition in training there now. From that side of things it's great to see, especially with their age profile too, these guys are young and have a fantastic future ahead of them.

"It's important that they know now that this is just step one, getting into the extended squad is just step one.

"And then getting into the match-day squad is step two, and then you've got to be looking to start and push to better yourself every time.

"That's the attitude they will adapt, they've already given that impression, and it's great for the squad.

"Competition for places drives everyone on and hopefully raises standards across the board."

Moore has just 23 senior Leinster appearances to his name since his provincial debut in April 2012.

The 22-year-old has racked up 18 of those in his breakthrough season though, and secured a new Leinster deal, snubbing interest from the likes of Aviva Premiership clubs Exeter and Harlequins.

The Castleknock College and Ireland Under-20s graduate is highly regarded in Irish Rugby Football Union quarters, and looks to have earned a first chance to impress under head coach Joe Schmidt.

Club-mate McGrath made his Ireland debut in the 40-9 November Test victory over Samoa, claiming man-of-the-match honours.

Ireland boss Schmidt is likely to make few changes from the starting line-up that lost out so agonisingly 24-22 to world champions New Zealand in Dublin in November.

Luke Fitzgerald is expected to partner Fergus McFadden on the wings when former Leinster coach Schmidt names his squad to face Scotland on Friday.

Ulster flanker Chris Henry should slot in for Sean O'Brien, who will miss four months' action after shoulder surgery, and that could free up a spot on the bench for the uncapped Cardiff Blues loose forward Robin Copeland.

Best expects Scotland to scrap and spoil for every shred on Sunday, admitting the visitors will punish any lack of accuracy and physicality at the breakdown.

"Their back row are very abrasive so you've go to roll up your sleeves and prepare for battle," said Best.

"You look at their pack, and the breakdown is massive.

"The back row will cause plenty of problems, but even Jim Hamilton and some of the front row, they are very dangerous over the ball if you let them get in.

"And it's going to be very tough to slow their ball down because they are big men, they carry hard and they hit rucks hard too.

"It's a great challenge against a big pack, but that brings pressure too, because you need to perform."