Injury-hit Newcastle's face a massive test of their mettle to keep their NRL season alive when they take on Canterbury at ANZ Stadium on Saturday.

The Knights will definitely be without hooker Matt Hilder and centre Junior Sa'u, while playmaker Jarrod Mullen and centre Adam MacDougall remain in doubt.

Mullen has a small rotator cuff tear in his shoulder but the club said he was better than a 50-50 chance after consulting a specialist.

MacDougall's knee injury is causing him problems and the 36-year-old confirmed on Friday he would retire at season's end after 16 years in the top grade.

"I suppose somewhat I have been in a state of denial because I have been doing it for so long," MacDougall said.

"It's a little bit surreal,and I think that is the best way to describe it."

The eighth-placed Knights' finals charge has stumbled with two straight losses and they could find themselves outside the eight by the end of the weekend.

If they drop the match against the Bulldogs and South Sydney upset Brisbane, Newcastle (currently 26 points) will be two points behind the Rabbitohs (26) and equal with Jim Dymock's side (24).

Next week's clash between the Knights and Souths looms as crucial regardless of results this weekend, with Newcastle's points differential plus-29 and the high-scoring Rabbitohs' minus-three.

Canterbury's differential of minus-64 means they will struggle to sneak in to the play-offs even if they down both the Knights and, next week, Canberra.

"We've been speaking about it being big games for us every week because we're on the tightrope I suppose so that will probably continue," Bulldogs captain Andrew Ryan said.

"That's the way it is, it's this time of the year where it's a bit hard for people so hopefully we can get a good win."

Ryan, who will also retire at season's end, nominated veteran sparring partner MacDougall and his brilliant wing partner Akuila Uate as the Knights' danger men.

"They've got a lot of strengths but their right side just to start with, Adam MacDougall and Uate out there, they've been in some red-hot form," Ryan said.

"There's danger all over the field, guys like (Kurt) Gidley, there's a lot of guys there so we need to be on defensively."

While the ANZ Stadium clash is crucial to Newcastle righting their ship, MacDougall admitted to having one eye on his battle with Test and Rabbitohs superstar Greg Inglis at Ausgrid Stadium next week.

"Next week is winner takes all, for-and-against is minimal," he said.

"No matter what happens (this week) I think they (the Rabbitohs) have the capacity to score a lot of points and it is winner takes all.

"Personally I am excited about the challenge of taking on arguably the greatest player in the modern game or the greatest centre in a long time.

"For me there is no greater test and I relish those opportunities."

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