The U20s take on Ireland at Donnybrook on Friday evening (ko 7.35pm) but will do so without the Glasgow Hawks' lock who has led the Scots to two victories in this season's Six Nations.
The Scots will also be without Andrew Davidson who is ruled out due to a concussion sustained in last weekend's defeat to France.
Glasgow's Academy Stage 3 players Matt Smith and Callum Hunter-Hill start for Scotland.
Scotland U20
15 Tom Galbraith (Melrose)**
14 Darcy Graham (Hawick)*
13 Rory Hutchinson (Northampton Saints)
12 George Taylor (Melrose)**
11 Ben Robbins (Currie)**
10 Adam Hastings (Bath Rugby)
9 Hugh Fraser (Heriot's)**
1 Murray McCallum (Heriot’s)**
2 Jake Kerr (Boroughmuir)**
3 Callum Sheldon (Leeds Beckett University)
4 Callum Hunter-Hill (Stirling County)**
5 Stephen Ainslie (Currie)
6 Scott Burnside (Boroughmuir)*
7 Matt Smith (Glasgow Hawks)**
8 Ally Miller (Melrose)**
Substitutes
16 Lewis Anderson (Ayr)
17 George Thornton (Bishop Burton College)
18 Adam Nicol (Stirling County)
19 Hamish Bain (Currie)*
20 Lee Scott (Ayr)
21 Ruaridh Dawson (Newcastle Falcons)
22 Robbie Nairn (Harlequins)
23 Ruairi Howarth (Gala)*
* BT Sport Scottish Rugby Academy stage 2 player
** BT Sport Scottish Rugby Academy stage 3 player