The Ospreys have been struck by a late blow ahead of their clash with the Scarlets after scrum-half Rhys Webb was ruled out due to illness.
Martin Roberts comes into the starting XV in his place with Richard Fussell taking his place among the replacements for the game in Llanelli.
Tom Grabham will now wear 21 and cover scrum-half, with Fussell wearing 23.
Ospreys (revised): 15 Dan Evans, 14 Hanno Dirksen, 13 Ashley Beck, 12 Josh Matavesi, 11 Aisea Natoga, 10 Dan Biggar, 9 Martin Roberts, 8 Tyler Ardron, 7 Justin Tipuric, 6 Dan Lydiate, 5 Alun Wyn Jones (c), 4 James King, 3 Dmitri Arhip, 2 Scott Baldwin, 1 Marc Thomas.
Replacements: 16 Sam Parry, 17 Duncan Jones, 18 Aaron Jarvis, 19 Rynier Bernardo, 20 Sam Lewis, 21 Tom Grabham, 22 Sam Davies, 23 Richard Fussell.
Date: Saturday, 3 January
Venue: Parc y Scarlets
Kick-off: 17.05 GMT
Referee: John Lacey (Ireland)
Assistant referees: Ian Davies (Wales) and Marty Lewis (Wales)
Television match official: Tim Hayes (Wales)