The New Zealander wants them to finish as the top Welsh team in the table and also stake claims for places for Wales' summer tour Tests against Samoa and Tonga.
Scarlets have secured a top-four finish and Ospreys are all but assured of qualifying for the play-offs.
"One of the team goals was to be the top Welsh region," said Pivac.
He continued: "So to finish top, we need a win on the weekend."
The Pro12 title will be decided after semi-final play-offs in which Scarlets or Ospreys will travel to Ireland to face either Leinster or Munster.
The leading Irish teams go into round 22 first and second in the table respectively.
The team finishing top will play the fourth-ranked team with second hosting third meaning, as things stand, Scarlets would go to Munster while Ospreys would be at Leinster later in May.
Pivac said the clash with the Ospreys, "is not a cup final", however, adding: "In isolation, it's one of our team goals is to finish top Welsh team on the ladder.
"We were able to do that last year and we want to replicate that.
"There's also the small matter of a tour to the southern hemisphere for Wales to play two Test matches.
"Part of our role is to get results for the club.
"It's also to help promote players to that next level so there's a lot to play for in this weekend's game."
Pivac also highlighted how finishing highest among Welsh teams can affect which group they would play in during the 2017-18 Champions Cup.
He said: "There is pressure. The top four is put to bed, but we certainly are looking at finishing as high up as we can because it impacts on the pool we have for Europe next year, which is important."
Wales lock Jake Ball and Scotland back-rower John Barclay are doubts to face their local rivals as the regular season ends.
Ball came off with a shoulder injury in Scarlets' win at Connacht on Saturday, and Pivac says he is "50-50" to be fit to face Ospreys.
Barclay was withdrawn before kick off in Galway after suffering a hamstring twinge in the build-up and Pivac says he will not be tempted to select any injured players.
He added: "We are selecting to achieve our team goals and to do that we're up against a strong Ospreys team who have similar goals, I would imagine.
"And their players are playing for positions on the tour as well so will be equally motivated.
"We'll be putting out the strongest team possible without being silly.
"If there are players carrying injuries we have that luxury of the semi-final to think about as well."
Scarlets won what was then called the Celtic League title in the first season of Welsh regional rugby in the 2003-04 campaign but they have not won it since.
Their most recent semi-final play-off appearance came in 2013, when they lost at that stage to Ulster.

Revenue for the three months to the end of September was 22.2bn yuan ($3.5bn; Â£2.3bn), up 32% from a year earlier.
Revenue from mobile devices grew particularly strongly.
The value of transactions conducted through the website totalled 713bn yuan, with the number of active buyers growing to 386 million.
"This was a great quarter for Alibaba Group, with strong growth across the board and particular outperformance in mobile," said chief executive Daniel Zhang.
"We are winning in mobile and remain focused on our top strategic priorities, including internationalisation, expanding our ecosystem from cities to villages and building a world-class cloud computing business."
Alibaba said it had increased the number of villages in China it offers sales and delivery services to by more than 4,000 during the quarter.
Growth outside of China has been more muted.
"The performance of Alibaba's international division is reasonable but far from spectacular," said Neil Suanders at retail analyst Conlumino.
"At retail level, sales were up by a fairly modest 14.8%. In our view, this underlines the fact that, despite its scale and its technical expertise, Alibaba continues to struggle in carving out a niche in crowded and competitive Western markets."
Scarlets boss Wayne Pivac has given his players a double target when they host Ospreys in the Pro12 on Saturday.
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Chinese e-commerce giant Alibaba has reported a sharp rise in sales as more customers spent money through the online retailer.