Wednesday's game is sure to prove as stern a test especially after the Ospreys went down 35-3 to the Blues last time out. The Scarlets hit back from that opening defeat with a 33-30 victory over the Blues and then hammered the Dragons 38-11 at Caerphilly three weeks ago.
In the other game, the Dragons and Blues meet at Virginia Park, Caerphilly with the Dragons seeking a first win of the season for coaches Gareth Baber and Jason Forster.
Scarlets v Ospreys (Llandovery 7.15)
Dragons v Blues (Abergavenny, 7.15)