Superstar winger Kiraz landed awkwardly on his left ankle fielding a kick late on Thursday night and needed assistance leaving the field at Accor Stadium.
Kiraz could eventually hobble without support from trainers but early fears are that he may have suffered a syndesmosis injury.
The 23-year-old came close to a NSW State of Origin debut this year and would be a significant loss for the Bulldogs in their fight for a first premiership since 2004.
"It doesn't look great. Hopefully it's just a rolled ankle but he'll get a scan," said Bulldogs coach Cameron Ciraldo.
If Kiraz is unavailable, either journeyman Enari Tuala or rookie Jethro Rinakama would need to be called into the third-placed Bulldogs' 17 at the most important point of the year.
Second-rower Jacob Preston scored the first hat-trick of his NRL career to help the Bulldogs kick clear after some resistance from the unrecognisable Panthers in the first half.
With an eye on finals, Ivan Cleary rested all but one man from the Panthers' last game, playing a side with only 398 games of first-grade experience and four debutants.
That number went to five when 18th man Jaxen Edgar was activated following game-ending concussions to Luke Sommerton and Sione Fonua.
But the Panthers held the gloves up to the premiership hopefuls Canterbury.
"I sort of threw them in the deep end really. They were coming off a five day turnaround too, most of those boys," said coach Cleary.
"Just right 'til the end, defensively in particularly, we just kept turning up for each other and doing the very best they could. I'm very proud."
Pre-match predictions of a Bulldogs mauling came to nothing as Ciraldo's side lacked polish with the footy.
"They prepared as well as they've ever prepared and for 60 minutes really went about a professional performance, the last 20 minutes was a little bit sloppy," the coach said.
Lachie Galvin put Josh Curran into space and then supported him for their first try, before a shift put Preston over for a 10-0 half-time lead.
Galvin put Preston in for his next two tries, with the second-rower breaking through three tackles on the way to his third.Â
Amid a form slump for regular fullback Dylan Edwards, off-contract Daine Laurie was Penrith's best, helping hold Sitili Tupouniua and Connor Tracey up over the line in consecutive tackles at one point.
In the second, he threw the bullet-like pass for Paul Alamoti to score the Panthers' only try.
But Penrith, for their grit in defence, never appeared a serious threat of piling points on, unable to create consistent opportunities or spend extended time up the other end of the park.
The Bulldogs are now guaranteed to finish either third or fourth, but leaping into the top two appears a bridge too far given Melbourne's superior points differential.
"Top four is a great achievement, but it's only the start of what we want to achieve," Ciraldo said.
Last on the ladder after 12 rounds, the Panthers can finish the regular season as high as fifth but seventh or eighth appears likelier.
