The Scarlets tackle the Dragons in the early game at 1pm and will be looking to rattle up the points against a side which has conceded the most points in the competition so far.
In what has been a vastly improved competition this season, the Dragons have scored just three fewer points than the current leaders but defence has proved their Achilles heel as they have shipped nearly double what the Ospreys have.
The Ospreys are aiming for a third title on the trot but they aren't taking anything for granted as they prepare for battle against the Blues at 3pm, said team manager Ade Howells.
"We know the Blues will come at us with all guns blazing so it's going to be tough," he admitted.
"They are a very good side and have some very dangerous backs who can cause some real damage while they have some very good forwards like No 8 Gemma Hallett so we will have to keep an eye on her.
"The fact that a good performance in front of the national selectors may earn a call up for the Six Nations is also an incentive and that is something that may have been in the back of the players' minds but our real focus is performing as a team on Sunday and not as individuals.
"We haven't really clicked as a team in our previous games this season so hopefully Sunday will be the day everything clicks into place and we can come away with a win. There are several permutations which could happen on the day so all three teams in with a chance of winning the championship will be doing their best to do so - that's testament to the work all the sides have put in and can only be good for women's regional rugby."
Blues head coach Nadine Griffiths said that her side will give it their best shot despite being ravaged by injury.
"As a squad we are really looking forward to Sunday, everything is still to play for. We are still struggling with a lot of injuries and Nia Davies' injury last weekend will be a blow to us," she said.
"Win or lose on the weekend as a management team we have had a great time coaching the squad this year and are very pleased with the talent on show."
WRU Women's Regional Championship
Llandarcy Academy of Sport, Sunday 15 Dec
1pm - Scarlets v Dragons
3pm - Blues v Ospreys