The slumping Warriors face a potentially season-defining fortnight after going a fourth-straight game without a win when beaten 14-8 by a gritty Newcastle.

One of the NRL pre-season favourites after last year's run to the preliminary finals, the Warriors are now 14th on the ladder one-third of the way into the season.

With just three wins from nine games, the biggest concern for coach Andrew Webster will be who they've dropped games to.

Beaten by St George Illawarra and Gold Coast in the previous two weeks, the loss to Newcastle marked their third straight against a team outside the top eight.

It comes ahead of a crunch fortnight when they face the competition's two form teams, the Sydney Roosters then Penrith, both in Australia.

Two more losses there would leave the Auckland-based club's finals hopes in early danger of slipping away.

"We can't look too far ahead, we've got to get confidence in what we're doing fast," Webster said.

"I don't think there's the same zip in our attack (as last year). I don't think we're as on-point with it or as clinical. We're making it harder for ourselves."

Sunday's loss was not without drama, with the Warriors denied a crucial penalty try that would have given them a half-time lead.

After a hapless opening 20 minutes where they gave away five penalties, made four errors and handed Newcastle an 8-0 lead, the Warriors got the game back to 8-6.

Winger Dallin Watene-Zelezniak then appeared to hand the Warriors the lead, only for him to drop a ball over the line while being tackled in mid-air by Greg Marzhew.

Shaun Johnson argued with referee Chris Butler that a penalty try should have been awarded, given Watene-Zelezniak seemed certain to score without the contact.

Butler agreed, but told Johnson it was against NRL interpretations for penalty tries to be given when players are tackled mid-air.

"The only reason he didn't score is because he got tackled in the air," Webster said.

"I don't understand if there's a clause for that particular play if you're attacking and tackled in the air, but it looked like he was deadset going to score for all money.

"I thought a penalty try is if someone is about to score, and they're not allowed to through a penalty."

The Warriors were then denied again after the break, Jackson Ford ruled to have obstructed Jackson Hastings in the lead up to a Watene-Zelezniak touchdown.

Making matters worse, star second-rower Kurt Capewell succumbed to a calf injury early and is now doubt for the crucial fortnight ahead.

For all the drama though, the Warriors simply weren't good enough and the Knights were gutsier.

After the Warriors drew level at 8-8 in the second half, the Knights hit the lead again when Daniel Saifiti burst through Mitchell Barnett and Te Maire Martin to score.

In contrast, the Warriors had three full sets on the Knights' line to win the game in the final 10 minutes, but Newcastle's defence never looked like cracking.

The Knights' win marked their second in a row since Kalyn Ponga went down with a foot injury, and took their win-loss record to 4-5.

"It's important whether KP was there or not," coach Adam O'Brien said.

"We've had most of our DNA all year ... But I'm really proud of that performance, especially defensively.

"That's what we want to be known for, that's a Knights footy team."