Scarlets number eight Rory Pitman scored the only try as Scarlets edged a tight 19-9 victory over Glasgow Warriors.
Table-topping Ospreys aim to continue their perfect start to the Guinness PRO12 season when they travel to Ulster.
Cardiff Blues are in a strong position to progress in the LV= Cup after a 19-13 triumph over Welsh rivals Scarlets.
Cardiff Blues academy manager Richard Hodges hailed the hard-fought nature of their 19-13 LV= Cup win over the Scarlets.
Four Welsh teams are in action on Friday in the second round of LV= Cup action.
Northampton Saints made it two wins from two in the LV= Cup with a 24-7 victory over Scarlets in an error-strewn contest in Llanelli.
Defence coach Alan Dickens admitted Northampton were boosted by two England internationals for the clash with Scarlets.
The second round of LV= Cup clashes get under way on Friday, with Scarlets taking on Northampton.
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