It was Priestland, on as a replacement, who slotted the crucial last-gasp penalty to snatch victory away at Zebre in round 19, a result that kept Scarlets' GUINNESS PRO12 top six hopes very much alive.
But while Pivac acknowledged the importance of Priestland's nerveless kick in Italy, the New Zealander insists his selection will not be based solely on one moment.
"You don't get much more pressure than the last kick," the Scarlets coach told Wales Online.
"Everyone knew it was full-time and we were going to win or lose the game, which would have probably seen us kiss goodbye to any European dream - there was a lot of pressure.
"When that kick went over we just sat in the stand for five or ten minutes after the game, wondering what we had just witnessed.
"It has been a tight call for some weeks, and we have selected the team the way we have for a number of reasons.
"Steve has done a pretty good job. By his own admission he did not have his best game against Zebre.
"Like we do every week, we look at the form and who we are playing and make a decision based on that."
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