Plotting a Rabbitohs victory over Cronulla on Saturday night, Demetriou is the first coach to succeed Bennett at a club and take a side into week two of the NRL finals.
In guiding Souths to a do-or-die semi-final, Demetriou has already out-performed the likes of fellow rookie NRL coaches Ivan Henjak, Steve Price and Anthony Griffin.
But these finals are far from Demetriou's first rodeo.
Since taking over as player-coach of English third-tier team Keighley in 2011, Demetriou has not known a year without finals football.
He helped the small club from West Yorkshire to promotion in his first year, before backing it up in reaching the playoffs in the Championship the following season.
The former centre then returned home to coach Northern Pride to two minor premierships in the Queensland Cup, before being Paul Green's assistant when North Queensland won the NRL in 2015.
A premiership with the Illawarra Cutters in the NSW Cup followed in 2016, before reaching the finals under Bennett at Brisbane and Souths between 2017 and 2021.
"Coaching in finals series, playing in finals series, it all helps," Demetriou said.
"It's about knowing what your good at. And then keeping it simple."
It's from that experience Demetriou also doesn't believe he has required too much adjustment during his first year as an NRL head coach.
"I don't think I have (changed) too much," he said.
"I think the reason I'm in this position is the things that I've done leading up to that and I've been able to stay true to that.
"The players have been outstanding. I can't wrap them enough.
"There's a lot of pressure on this team going into the start of the season for a multitude of reasons."
Players have also seen Demetriou as his own man.
While he has long been seen as Bennett's successor at Brisbane and then the Rabbitohs, Souths players believe Demetriou is more a product of his own round-about journey.
"A lot of JD is just who he is," hooker Damien Cook said.
"That's what he's learned on his journey of coaching through reserve grade, coaching different teams, also playing over in England.
"He just understands what players have gone through as well and can relate to them
"That's why I think a lot of these boys go out there and play for him."
Cook said the way Demetriou had stuck by rookie halfback Lachlan Ilias was the best evidence of that.
"He put him in there and just left him all year when you see some clubs changing everyone," Cook said.
"That's the trust and belief he puts in the squad
"Credit to JD, just how he can get the best out of his players. He has our backs all the time."
DEMETRIOU'S 12 YEARS OF FINALS FOOTBALL
Keighley 2011: Won third-tier promotion playoffs (player-coach)
Keighley 2012: Championship finalists (player-coach)
Northern Pride 2013: Queensland Cup finalists (coach)
Northern Pride 2014: Queensland Cup premiers (coach)
North Queensland:- NRL premiers (assistant)
Illawarra Cutters 2016: NSW Cup premiers (coach)
Brisbane 2017-18: NRL finalists (assistant coach)
South Sydney 2019-21: NRL finalists (assistant)
