Flanker Will Boyde will make his Champions Cup debut for the Scarlets when they run on to face the Northampton Saints at Parc y Scarlets on Saturday.
The 21-year-old has made six appearances in the Scarlet jersey, his only starting XV spot coming in the LV= Cup clash against London Irish in January 2015.
The only other change to the pack sees Aaron Shingler returning to his favoured blindside flank.
Head Coach Pivac has made three changes to the backline that faced Racing 92 last Sunday. Steve Shingler moves from outside half to inside centre with Aled Thomas coming in at fly-half. Winger Tom Williams makes a return from injury to line-up alongside DTH van der Merwe and Michael Collins in the back three.
Speaking ahead of the final pool game of the Champions Cup campaign Pivac said: "We're pleased to be welcoming some boys back this weekend. We're also playing at home. There has been a huge emphasis on rectifying some of the wrongs from last week because we need a strong and improved performance to take into the Connacht game when the PRO12 gets back underway next weekend.
"Northampton are still in with a chance of qualifying. I would expect them to come here and want to perform.
"We're looking for a big performance no matter what side they put out. We'll be tidying up our defence and trying to get somewhere near parity in terms of possession and territory.
"You want the players to be hurting after results like last weekend’s so that the next opportunity they have to wear the jersey they right the wrongs."
Meanwhile, the Saints head to Parc y Scarlets still in contention for a quarter-final spot, and have made five changes to the starting line-up that will run out to face the Scarlets.
In the backs Jamie Elliott, Harry Mallinder, Stephen Myler and Tom Kessell come in, with Sam Dickinson returning to the back row.
Form: Jim Mallinder's men kept themselves in the race for the last-eight with a 19-15 victory over Glasgow Warriors last weekend. The battling win gave the Saints 14-points from five rounds of Champions Cup action. ASM Clermont Auvergne and Stade Francais also go into the final round with 14 points, and Wasps have 15 ahead of their make-or-break clash with Leinster Rugby. A bonus-point win would give the Aviva Premiership side a huge chance of qualification, but the Scarlets are desperate to register a first victory. Scarlets suffered their record European defeat when Racing 92 thrashed them 64-14. But Scarlets wing Steffan Hughes wants to finish the Pool 3 campaign with a win.
Scarlets: 15 Michael Collins, 14 Tom Williams, 13 Regan King, 12 Steven Shingler, 11 DTH van der Merwe, 10 Aled Thomas, 9 Gareth Davies, 8 Morgan Allen, 7 Will Boyde, 6 Aaron Shingler, 5 Maselino Paulino, 4 Tom Price, 3 Samson Lee, 2 Ken Owens (c),1 Phil John
Replacements: 16 Kirby Myhill, 17 Dylan Evans, 18 Rhodri Jones, 19 Lewis Rawlins, 20 Tom Phillips, 21 Aled Davies, 22 Josh Lewis, 23 Steff Hughes
Northampton: 15 Ben Foden, 14 Jamie Elliot, 13 George Pisi, 12 Harry Mallinder, 11 George North, 10 Stephen Myler, 9 Tom Kessell, 8 Sam Dickinson, 7 Tom Wood, 6 Jamie Gibson, 5 Christian Day, 4 Courtney Laws, 3 Paul Hill, 2 Dylan Hartley (c), 1 Alex Waller
Replacements: 16 Mikey Haywood, 17 Ethan Waller, 18 Gareth Denman, 19 Michael Paterson, 20 Jon Fisher, 21 Lee Dickson, 22 JJ Hanrahan, 23 Luther Burrell
Date: Saturday, January 23
Venue: Parc y Scarlets
Kick-off: 17:30 GMT
Referee: Pascal Gauzère (France)
Assistant Referees: Maxime Chalon (France), Jean-Luc Rebollal (France)
TMO: Jean-Marie Piraveau (France)