Cordner, who has been sidelined with high-ankle sprain syndesmosis since last month, is on target to be back in action for the preliminary final should the Roosters beat Manly and secure a week off.
But the 21-year-old NSW back-rower said his side would sorely miss Waerea-Hargreaves' aggression against a vastly experienced Manly side competing in a ninth successive finals campaign.
"It was Sonny Bill's best game of the year against Souths, but I thought Jared was unreal for us," Cordner said.
"He just showed again why, in my opinion, he's currently the best front-rower in the game. He's a massive loss for us."
It is the second time Waerea-Hargreaves has been suspended this season after being given a five-week layoff following his sending-off against the Sea Eagles for a shoulder charge to the head of George Rose.
The Roosters lost two of their five games during his absence but Cordner said it proved they could cope without him.
"But we have played and won without Jared before, but the boys will definitely have to step up and share the workload as he is a vital part of the team," he said.
Cordner said he was making good progress from the tightrope surgery he underwent to reattach the ligaments to the bone using wire inside the joint. However, he said watching from the sidelines was proving to be as hard as the punishing rehabilitation he's undergoing to get him back on the field.
"I am a week away from running, I am hoping to get two weeks of running under my belt before I play," he said.
"It's been pretty heavy stuff with the physio, but I know it's going to get me where I want to be.
"With the team we have and the chance we have of winning something this year, the timing of the injury was pretty shattering.
"Last Friday was the hardest game I had to watch ... it made me hungrier to get out there as it was semifinal football.
"Watching Jared and Sonny going at it in front of that big crowd ... it's the games you want to play in."
5-Sharks v 8-Cowboys
Sydney, tomorrow, 6pm
North Queensland's Lazarus-like surge started when coach Neil Henry put them in a room and told them his time had come to an end.
Beaten by the Brisbane Broncos seven weeks ago, sporting a 6-12 record and three wins out of the top eight, the Cowboys board had tapped Henry on the shoulder with a year left on his contract.
Instead of calling it quits immediately, the 52-year-old got his troops together and told them his fifth year in charge would be his last. But it didn't mean they'd be going through the motions for the rest of 2013.
Six straight wins later they enter the NRL finals as the form team of the competition, complementing their flamboyant attacking game with a series of second-half defensive shutouts.
Seasoned second-rower Gavin Cooper says Henry's honesty and commitment to what appeared a lost cause sparked the turnaround.
"Once everyone knew where they stood, Neil got us in a room and told us what was going on," Cooper said. "He wanted us to hear it from him first. He said the board wanted him to serve out the season and he was thankful for that.
"He wanted to go out on the highest note possible. Everyone has bought into that and everyone is firing on the same page."
The Cowboys' results under the deposed Henry are in stark contrast to Canberra, who failed to win another match after David Furner was sacked with three rounds to play when they were ninth.
Cooper says a release of pressure combined with a desire to throw caution to the winds and play with confidence paved the way for a 30-12 boilover of high-flying Souths five days later.
"We definitely knew we could make the eight - I looked at the draw and there was a lot of teams ahead of us playing each other - so there was always that belief," the 28-year-old said.
"We started to go out there and play that carefree footy the Cowboys are known for. We'd gone into our shell a bit after a run of a few losses.
"We're at our best offloading and running the ball, but we'd gone to a robotic style of footy."
Their cavalier approach makes North Queensland a premiership dark horse, especially considering their miserly defence - conceding just three second-half tries in the last five games.
"The [opposition's] defence will be a lot more intense in the finals but if we're going to give any shake to this competition that's the way we have to play with the ball," Cooper said.
6-Bulldogs v 7-Knights
Sydney, Sunday, 6pm
Canterbury may have come off second best to elimination final opponents Newcastle twice this season, but coach Des Hasler says NRL finals are a different ball game.
The Bulldogs head into their clash with the Knights at ANZ Stadium on Sunday having copped an 8-44 pummelling from the Knights back in May and a 12-18 defeat in July.
"Most sides view it at this stage now in finals, [that] what happened throughout the year probably doesn't count for much," Hasler said on Thursday.
"Most of the sides prepare and play and react in such a way that they play in the moment. Those two games are well and truly gone."
The odds are against the sixth-ranked Bulldogs going one better than last year's grand final berth by winning the title - no club in NRL history has won the premiership from outside the top four under the current finals format.
Hasler was confident his team could prove the statistics wrong as he prepared to field a near full-strength side after giant forward Sam Kasiano and elusive fullback Ben Barba made their returns from long injury layoffs last week.
However, there are some injury clouds still circling for forwards Frank Pritchard and Greg Eastwood.
Knee and groin problems threaten Pritchard's return after two weeks' suspension for a shoulder charge while Eastwood is still recovering from a broken hand.
"They're a very good chance of not playing," Hasler said. We've got the Sunday game so we'll give those players as much time as we can.
"But we want to take in a strong squad.
"Sam Kasiano came through well last week. So we've got a lot of experience."
2-Rabbitohs v 3-Storm
Sydney, tonight, 9.45pm
Melbourne Storm are still keeping their starting five-eighth for the NRL final against South Sydney under wraps with Brett Finch and Gareth Widdop both training in the role.
The pair shared the position in the Storm's final training run behind closed doors before their flight to Sydney ahead of their qualifying final tonight at ANZ Stadium.
Finch has been under an injury cloud after damaging his sternoclavicular joint midway through the Storm's golden-point win over Gold Coast last round. England international Widdop, meanwhile, is ready for his NRL comeback after recovering from a dislocated hip in late June.
He played in the Storm's feeder team in the Queensland Cup last Sunday.
Teammate Ryan Hoffman said Finch, as the incumbent, would start if he was declared 100 per cent.
"Finchy's named there so I don't think anyone else will be wearing No6 but him," Hoffman said.
"Finchy and Gaz [Widdop] both trained in that five-eighth position so we're not sure of the decision Craig [Bellamy's] going to make. They're both fit and raring to go."
Hoffman said Finch completed some contact work during the session, with his injury certain to be targeted by the Souths forwards should he play.
- AAP
