Liam Williams has been ruled out of Wales' Six Nations opener against Italy as he continues to recover from ankle surgery, but the Saracens fullback should be fit for the rest of the tournament.
Williams, who will move to Scarlets at the end of the season, has not played since suffering an ankle injury in training ahead of Wales' World Cup semifinal defeat against South Africa in October.
However, teenager Louis Rees-Zammit is set to be fit for the curtain-raiser after recovering well from a knock suffered in Champions Cup action for Gloucester at the weekend.
"Liam is on for round two of the competition, he won't make the first game," Pivac said at the launch event of the Six Nations.
"Louis picked up a bump last week, he's worked well with the medical team and he'll hopefully be training this morning."
Rees-Zammit earned his spot in the Wales squad following a series of electrifying performances for Gloucester in the Gallagher Premiership, which earned him the league's player of the month award for December.
He will be competing with the likes of George North, Josh Adams, Jonah Holmes and Owen Lane for a spot on the wing for the Italy clash on Feb. 1, and Pivac is very excited to be working with the 18-year-old.
On Rees-Zammit, Pivac said: "As an individual, meeting Louis for the first time as opposed to speaking over the phone, he's a young man that is confident and he should be because he's playing well."
Pivac expects Williams to be fit for Wales' trip to Ireland on Feb. 8, while Owen Watkin is also likely to be fit for that match.