Trent Robinson has backed the NRL's concussion protocols, despite a bunker error forcing the Sydney Roosters to apply to have Sam Walker cleared for the blockbuster against Penrith.

Just after halftime in last Friday's 48-6 win over South Sydney, the bunker's independent doctor ordered Walker from the field after he bounced out of a tackle on Jack Wighton, appearing dazed.

It became clear Walker was not concussed after the Roosters' medical staff assessed him in the sheds.

But because the bunker's independent doctor had deemed the halfback to have suffered category-one head injury symptoms, he could not return to the game.

The Roosters applied to have the NRL reassess the halfback, who has since been approved to face reigning premiers Penrith on Thursday night.

"To go to a category one we felt was too far, and obviously the NRL saw that, which was a positive process," Robinson said.

It is not the first time a club has successfully applied to have a category-one designation reassessed.

Last season, Manly was permitted to play Tom Trbojevic inside the mandatory 11-day stand-down period after the NRL quashed a category-one ruling by the bunker from State of Origin I.

NRL football boss Graham Annesley backed the independent doctor system on Monday, saying only the bunker could examine multiple camera angles of a possible concussion.

Robinson struggled to hide his frustrations with the category-one call immediately after fulltime last week, but was more supportive on Wednesday.

"It's a good process because they are independent," he said of the bunker's doctor.

"It's pretty clear that orange shirts (club doctors) can't see anything and they have got a bias towards their team.

"It's very rare, but when they over-correct a little bit like they did, I think there's a couple of occasions there where it's been reversed.

"That was a positive because Sam wasn't concussed, or wasn't even close. He had a sore neck, but not a sore head."

The bunker's call did not ultimately impact Friday night's result; the Roosters led 24-0 when they lost Walker and never looked a chance of capitulating.

But Robinson said it was important to have been on the front foot for the sake of future incidents.

"It could've been costly within the game," he said.

The Roosters have lost representative prop Lindsay Collins and utility Sandon Smith for the Panthers game after both picked up injuries in the win over Souths.

Collins clutched at a hamstring late in the match and needed to come off, but has since resumed running and could return as soon as the round five clash against Canterbury.

"There's some positive signs already, but (he's) obviously not ready to play," Robinson said.

Smith played the entire second half with a hyper-extended elbow, but will now miss between four and six weeks. Luke Keary returns from concussion to reclaim the five-eighth spot.

Robinson said Billy Smith's prognosis was less rosy after he rolled his ankle contesting a high ball in the NSW Cup loss last Friday.

The luckless centre, who had ruptured his anterior cruciate ligament three times by his 23rd birthday, will miss "a couple of months" after undergoing surgery.

"It's disappointing," Robinson said of Smith's latest injury.

"We've been in a relatively good spot injury-wise, but just a couple of annoying ones there."