The co-captain and veteran hooker will mark the major milestone at Sunday's game against Parramatta, having endured a tumultuous week overshadowed by a highly publicised bust-up between his head coach and one of his strongest teammates.
But the now-resolved Adam Doueihi-Benji Marshall snafu won't take the shine off a glittering career peppered with trophies at South Sydney and Penrith - just not with his current club.
Asked about his decision to leave a dominant Panthers side in 2022, Koroisau had no regrets.
"(It) didn't change anything, even with everything that's gone down," he said.
"Understanding I've been through some hard times here ... that I can still help people regardless of how we're tracking and just trying to play some good footy.
"There's a lot of noise that comes from the outside, but us in these four walls, we've been pretty good."
The 33-year-old front-rower debuted at the Rabbitohs during their premiership triumph in 2014.
He says he only vaguely remembers his maiden NRL game that year against Canberra, when South Sydney went down 30-14.
"It was all a bit surreal, I'm still thinking about it now. I'm not even the same person," he said.
"A lot of growing up and maturing in that time, but also still the little kid that just dreamed of playing NRL."
While his 12 years of first-grade footy had altered him off the field, Koroisau said he had stayed glued to his signature crafty playing style.
"I don't know if much has changed to be honest," he said on Friday.
"Trying to get a bit more trickery in my game .. but still just putting my body on the line and just defending."
The 16th-placed Tigers are no longer gunning for a finals berth after a 56-10 flogging by Canberra on Saturday left their hopes for a fairytale top-eight tilt in tatters for the 15th consecutive season.
It will be a dead-rubber contest at Sydney's CommBank Stadium against the 15th placed Eels who on a miserable run of form.
But Parramatta may carry some momentum into Sunday's fixture after coming agonisingly close to stunning red-hot minor premiership favourites Penrith last week.
The basement-dwellers held the lead until the 57th minute and kept the Panthers to a 24-18 scoreline in what proved an unconvincing victory.
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