Skipper Josh Macleod returns from injury to lead a side containing debutant Fletcher Anderson as Scarlets take on Harlequins in a friendly at the Twickenham Stoop on Friday evening (19:45).
Macleod has been absent since the opening round of the URC because of a pectoral muscle injury.
Also back in the ranks is Wales international Eddie James, who has recovered from a long-term back issue.
Head coach Dwayne Peel has named a strong squad in preparation for the resumption of URC action at home to Glasgow Warriors a week on Saturday, with a 28-strong group heading to West London.
Ellis Mee, Jac Davies and Tomi Lewis make up an attacking back three. In midfield, James combines with fellow Wales international Johnny Williams. Sam Costelow and Gareth Davies provide an experienced partnership at half-back.
The front row consists of Kemsley Mathias, Marnus van der Merwe and Archer Holz, while Dan Gemine packs down alongside Sam Lousi in the second row.
Fletcher Anderson starts at No. 8 in a back-row that also contains Macleod and Jarrod Taylor.
A 13-man bench includes 17-year-old Wales U19s fly-half Carwyn Leggatt-Jones, who is set for his Scarlets senior debut and second row Kai Jones, another who played for Wales U19s in Paris last weekend.
Scarlets team to play Harlequins, Friday, November 21 (19:45)
15 Ellis Mee; 14 Jac Davies, 13 Johnny Williams, 12 Eddie James, 11 Tomi Lewis; 10 Sam Costelow, 9 Gareth Davies; 1 Kemsley Mathias, 2 Marnus van der Merwe, 3 Archer Holz, 4 Dan Gemine, 5 Sam Lousi, 6 Jarrod Taylor, 7 Josh Macleod (capt), 8 Fletcher Anderson.
Reps: 16 Harry Thomas, 17 Sam O’Connor, 18 Henry Thomas, 19 Kai Jones, 20 Osian Williams, 21 Dane Blacker, 22 Carwyn Leggatt-Jones, 23 Macs Page, 24 Ioan Nicholas, 26 Ben Williams, 27 Gabe McDonald, 29 Josh Morse, 30 Harri O’Connor.