The west walians are five points off the Guinness PRO14 play-off places in Conference B with six games left to play.
"This is a must win game," said Pivac.
"It's very important from a Scarlets and a Wales point of view that we are playing in the Champions Cup next season. I think we have to beat the Cheetahs and if we don't it means other results have to go our way.
"That would build a lot of pressure on us. For us it's a home game and we've got a proud record at home so we want that to continue.
"I'm pretty sure the boys will be up for the game and fully motivated because a lot of them were disappointed with their individual performances against Benetton."
The Scarlets have also been boosted by the availability of Wales squad members Wyn Jones, Ryan Elias and Jake Ball who will captain the side.
But Pivac is wary of a Cheetahs side who are fighting for a play-off place in Conference A.
"The Cheetahs kick the ball the least so they like to play, they have some genuine speed, they score a lot of points and they concede a lot of points," said Pivac.
"We have to make sure we win those physical exchanges when we have ball in hand so we can unleash our backs who we believe are pretty potent."