Hooker Ryan Elias takes over the captaincy from Macleod who is going through head injury return-to-play protocols following a knock in the 21-17 victory at the Arms Park against Cardiff.
Macleod is replaced by the returning Taine Plumtree in one of four changes from the side that beat Cardiff.
Ellis Mee switches to full-back in Murray’s absence with Joe Roberts named on one wing with Tom Rogers continuing on the other.
In form Eddie James who has two tries in his last two appearences against Mark Jones’ side continues in midfield with Johnny Williams, whilst Joe Hawkins again partners veteran Gareth Davies at half-back with Costelow on the sidelines.
Up front, Mathias misses out because of a groin issue so Alec Hepburn starts at loose-head alongside Elias and the fit-again Archer Holz.
Evergreen Jake Ball and Sam Lousi are again named in the second row engine room, while Plumtree has overcome a rib injury and comes in for Macleod at openside.
On the bench, loose-head prop Josh Morse is set for his URC debut, as well as fly-half Elis Price, who was an unused replacement against Cardiff.
Scarlets XV to face Ospreys:
15 Ellis Mee, 14 Tom Rogers, 13 Eddie James, 12 Johnny Williams, 11 Joe Roberts; 10 Joe Hawkins, 9 Gareth Davies; 1 Alec Hepburn, 2 Ryan Elias (captain), 3 Archer Holz, 4 Sam Lousi, 5 Jake Ball, 6 Max Douglas, 7 Taine Plumtree, 8 Fletcher Anderson.
Replacements:
16 Marnus van der Merwe, 17 Josh Morse, 18 Henry Thomas, 19 Tristan Davies, 20 Jarrod Taylor, 21 Archie Hughes, 22 Elis Price, 23 Macs Page.
[Lead image: Scarlets Rugby]
