At the other end of the experience spectrum Ross Ford will become the most-capped Scotland player in history.
The hooker will overtake the record held by former full-back and all-time top points' scorer, Chris Paterson, when he makes his 110th appearance in Suva, some 13 years since his debut against Australia at Murrayfield.
New Zealand-born Nick signed for Glasgow Warriors at the start of the season having impressed for Stirling County as a BT Sport Scottish Rugby Academy player.
He went on to make 21 appearances for the club since his March 2016 debut and enjoyed a fine season with the Scotstoun club.
Scotland Head Coach, Gregor Townsend, said: "It's a great storyline that we have Nick making his international debut at the same time as Ross will make history and become the most capped Scot of all time."
The inclusion of Ford and Grigg are two of 12 changes to the starting line-up, which sees the entire bench made up of players who kicked off last weekend's win over Australia (24-19).
Their rotation accommodates a new back-three, which features a first tour appearance for Ruaridh Jackson at full-back, and returning wings Tim Visser and Damien Hoyland - both try scorers in Scotland's first test victory over Italy in Singapore.
A new half-back pairing of Henry Pyrgos and Pete Horne starts the match - the latter a replacement for recent British & Irish Lions recruit Finn Russell - while the sole returnee in the backs, Duncan Taylor, partners Nick Grigg in midfield.
In the pack Alex Allan and back-row John Hardie will make their first appearance of the tour - the latter having recovered from the back strain that forced his late withdrawal from the Italy test.
Allan is joined by the record-breaking Ford and returning tighthead prop Willem Nel in the front-row, while Hardie is accompanied by captain John Barclay and the incoming Josh Strauss in the loose forwards.
The starting line-up is completed by the inclusion of lock Tim Swinson, who switches places with Ben Toolis to partner Jonny Gray in the boiler house.
Townsend added: "It's been a very good tour so far. The games have gone well with two positive results and the players have enjoyed their time together.
"In terms of selection, we are looking at where the guys are in terms of form and their physical status, as well as seeking to give players opportunities.
"It's a really strong team with a bench that can up the tempo of the game. We're looking forward to seeing them play.
"Fiji have improved a huge amount over the past few years and did very well to find a way to win against Italy last weekend. They are excellent from unstructured play and have a number of very evasive players throughout their squad.
"We have to make sure that we're accurate when we play our attacking game and whenever we kick. Fiji will come alive if we're loose in those areas. It should be a cracking Test match."
Scotland team to play Fiji at the ANZ Stadium, Suva
Saturday (24 June, ko 2.30pm, 3.30am BST) - streamed live on www.scottishrugby.org
15 Ruaridh Jackson (Harlequins)
14 Damien Hoyland (Edinburgh Rugby)
13 Nick Grigg (Glasgow Warriors)
12 Duncan Taylor (Saracens)
11 Tim Visser (Harlequins)
10 Peter Horne (Glasgow Warriors)
9 Henry Pyrgos (Glasgow Warriors)
1 Alex Allan (Glasgow Warriors)
2 Ross Ford (Edinburgh Rugby)
3 Willem Nel (Edinburgh Rugby)
4 Tim Swinson (Glasgow Warriors)
5 Jonny Gray (Glasgow Warriors)
6 John Barclay CAPTAIN (Scarlets)
7 John Hardie (Edinburgh Rugby)
8 Josh Strauss (Sale Sharks)
Substitutes:
16 Fraser Brown (Glasgow Warriors)
17 Gordon Reid (London Irish)
18 Zander Fagerson (Glasgow Warriors)
19 Ben Toolis (Edinburgh Rugby)
20 Hamish Watson (Edinburgh Rugby)
21 Ryan Wilson (Glasgow Warriors)
22 Ali Price (Glasgow Warriors)
23 Greig Tonks (London Irish)