NRL assistant referee Bill Harrigan has backed the controversial decision of onfield referee Sean Hampstead in Newcastle's 22-12 victory over the Bulldogs at ANZ Stadium.

Bulldogs coach Steve Folkes said Hampstead's decision to not go to the video referee left him "dumbfounded".

Two points outside the top eight before this weekend, Newcastle remain in the finals race.

The loss delivered another big blow to the injury-ravaged Bulldogs, who started the round in 14 points and could now be without winger Matt Utai for up to two months, after he suffered a posterior cruciate knee problem.

The Knights controlled the ball better in a scrappy game scoring four tries to two, with debutant Junior Sau, crossing twice for the visitors.

A finely balanced contest was effectively decided in a crucial two-minute period in the second half.

Newcastle led 10-6 in the 54th minute when Bulldogs skipper and second-rower Andrew Ryan dived over Newcastle five-eighth Jarrod Mullen in a contest to ground a pass from the Knights' Chris Bailey.

Hampstead ruled Mullen had grounded the ball after getting confirmation from sideline official Matt Cecchin and awarded the Knights a line dropout.

Within two minutes Sau scored his second try to set up a 16-6 lead and send the vastly depleted Bulldogs crashing to their eighth loss in 12 games.

Replays of the controversial incident suggested it wasn't clear-cut and Folkes believed the matter should have been referred to Harrigan who was the video referee for the game.

"You see so many decisions week to week go up to the video referee and to see something like that not sent up there, I was just dumbfounded," Folkes said.

"It was a turning point. If you go to the video ref, they probably don't go the length of the field and score from the next set of six.

"There's no doubt decisions like that eat away at you."

Hampstead didn't talk to the media after the game, but after watching frame-by-frame footage, Harrigan said he would have agreed with the match referee's call had he been asked to arbitrate on the matter.

"Hampstead is only a couple of metres away. He believed it was grounded and his touch judge confirmed it, so he ruled grounded and he didn't need to check it," Harrigan said.

"Had he sent it up and I had the opportunity to see all the replays and do frame-by-frame, I would have supported their decision."

Newcastle coach Brian Smith felt it was a waste of time commenting on the contentious decision.

"It doesn't do me or the game any good, we could spend our time having a party or something instead," Smith said.

He conceded it wasn't a particularly flashy effort from his team, which was missing NSW Origin representatives Danny Buderus, Steve Simpson and Kurt Gidley.

"It was one of those butt ugly awful nights to play footy, the guys were never going to win playing perfect footy," Smith said.

"It was a lot of hard work and effort on a greasy night."

The Knights led 10-6 at the break following converted tries to wing James McManus and Sau, while Utai crossed for the Bulldogs.

Following Sau's second try, Newcastle bolted to a 22-6 advantage after veteran centre Adam MacDougall bustled his way over the Bulldogs' stripe.

Fullback Nick Youngquest scored a late try for the Bulldogs, who earlier in the evening confirmed hooker Corey Hughes would join the Sharks next season.

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