The Sydney Roosters’ premiership hopes have suffered a devastating blow, with star halfback Sam Walker ruled out for the remainder of the season after scans confirmed a high-grade syndesmosis injury.

Walker will undergo season-ending surgery this week after suffering the injury during the Roosters’ 26-12 loss to the Dolphins at Allianz Stadium on Saturday night, according to CODE Sports.

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The 24-year-old hobbled from the field in the 53rd minute after his ankle was caught awkwardly in a tackle involving Dolphins forward Kulikefu Finefeuiaki.

The Roosters had been anxiously awaiting the results of scans, with coach Trent Robinson initially holding out hope Walker could return at some stage during the finals.

Instead, the worst-case scenario has been confirmed, leaving the Tricolours without their star playmaker for their premiership campaign and facing a major selection headache heading into September.

It is another crushing setback for Walker, whose season has now been ended prematurely for the second time in three years.

The incident occurred when Finefeuiaki’s knees were already grounded before he slid and made contact with Walker’s foot.

The Bunker reviewed the tackle but ruled there was no hip drop or foul play involved.

Walker immediately appeared in significant discomfort and eventually limped from the field, with fears quickly emerging that he had suffered a syndesmosis injury.

During the Cowboys and Tigers’ clash later on Saturday, Fox League commentator Dan Ginnane revealed the Roosters believed their halfback had suffered a syndesmosis injury.

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Speaking before the results of Walker’s scans were known, Robinson confirmed his halfback had been sent for further assessment.

“He’s gone for scans,” Robinson said post-game, with a final diagnosis expected within hours.

Asked whether the club feared Walker had suffered a high ankle injury, Robinson said: “Possibly, yeah. We’re thinking that.”

At that stage, the severity of the injury remained unclear and Robinson refused to speculate on what Walker’s potential absence could mean for the Roosters’ finals campaign.

“Yeah, look they’re hypotheticals,” Robinson said.

Captain James Tedesco was similarly hopeful the injury would not prove serious.

“Yeah, well we don’t know how severe it is yet, so hopefully it’s not too bad,” Tedesco said.

“But it’s one of those ones you get caught in the tackle. I had a similar one as well, so yeah, it’s tough, hopefully it’s not too long.

“We’ll see how it is, but again, I think everyone’s disappointed with our performance and that injury as well.”

Those hopes have now been dashed after scans confirmed the high-grade syndesmosis injury and the need for surgery.

Even before the diagnosis was confirmed, the immediate reaction to Walker’s injury painted an ominous picture.

“Walker has fallen down, Walker went down. This looks very bad for the Roosters, this is such a moment here, Walker in pain,” commentator Andrew Voss said on Fox League’s Super Saturday coverage.

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League great Michael Ennis immediately recognised the potential ramifications for the Roosters’ season.

“That has silenced the Roosters fans here at Allianz… wow, the Roosters season hanging by a thread here,” Ennis said.

Fox League’s Cooper Cronk then outlined what proved to be the worst-case scenario facing Walker and the Roosters.

“Best case scenario it’s two weeks and he will be fine, worst case he will require surgery and the season is done,” Cronk said.

“Sam Walker and the Roosters will be doing everything possible to get him back because his reaction to me was more than just a week or two, the way he was banging on the ground.

“Hopefully not because it’s a big curveball for the Roosters season.”

Sam Walker of the Roosters walks off injured.Source: Getty Images

The confirmation Walker will require surgery means Cronk’s worst-case scenario has now become reality, leaving the Roosters to find a way forward without one of their most important players.

Walker wasn’t the only Roosters player to leave the field during Saturday night’s defeat, with hooker Reece Robson also going off injured in the dying stages.

However, Robinson was confident his No.9 would avoid an extended stint on the sidelines after an awkward head clash.

“He put his head down to get it… and he just got his head crunched,” Robinson said.