By Jasper Bruce in Sydney

The Sydney Roosters’ NRL premiership hopes have been rocked after star halfback Sam Walker, Brandon Smith and Victor Radley were injured in a stunning 14-12 loss to Canberra.

Walker is suspected to have injured the anterior cruciate ligament in his left knee after pulling up sore attempting to tackle Simi Sasagi in the in-goal 12 minutes into Sunday’s game.

Three staffers attended to Walker and initially called for a stretcher before the playmaker regained his footing and left the field at Allianz Stadium, albeit with assistance and in severe pain.

Walker, who was troubled by ACL issues last year, is now all but guaranteed to finish this season on the sidelines and leave the third-placed Roosters to defy history in pursuit of a premiership.

In the NRL era, no side has won the grand final without their first-choice halfback.

Sandon Smith is the man most likely to join Luke Keary in the halves on the run through September.

Still reeling from the Walker blow, the Roosters were forced to reconfigure again after Canberra’s Elliott Whitehead crunched Brandon Smith’s right leg in a hip-drop tackle just before half-time.

The hooker writhed on the turf in agony before also leaving the field between two trainers with a suspected knee injury.

Second-rower Radley joined Smith and Walker in the casualty ward with left shoulder damage following a tackle from Joe Tapine and Adam Cook 10 minutes after half-time.

Fellow forward Nat Butcher returned a category-one head injury assessment in the second half so is likely to miss next week’s match against South Sydney but is expected to return for the finals.

Raiders captain Whitehead was sin-binned twice on Sunday, first for the shot that injured Smith and then for swinging a boot at the ball while it was in Angus Crichton’s grasp.

He had earlier been integral to the Raiders’ surprise 10-2 half-time lead, crashing over from a Danny Levi pass out of dummy half before throwing the offload that handed Sasagi the Raiders’ second try.

When Xavier Savage tore away down the right edge following a Michael Jennings error, the Raiders were up 14-2 and daring to dream.

Daniel Tupou slid over on the left wing soon after Whitehead’s second dismissal, with the Roosters finally shaking off uncharacteristic execution issues.

When Keary picked Tupou out with a fifth-tackle kick in the final seconds, the Roosters had a chance to equalise with a sideline conversion after the siren.

But part-time kicker Keary had his strike waved away and the Raiders held on for a pulsating victory.

Canberra have now ambushed premiership fancies Penrith and the Roosters inside two weeks but their inferior for-and-against leaves them as only a mathematical chance of making the finals.

Their likeliest path to qualification is beating St George Illawarra next week and hoping Newcastle and the Dolphins draw.

Raiders fan favourite Jordan Rapana looks to have played his last NRL game after suffering a fractured cheekbone laying a try-saving tackle on James Tedesco in the first half.

Rapana appeared to wear Tedesco’s elbow in his face as he tackled his rival fullback mid-air and is unlikely to feature again before joining Super League side Hull FC next year.