The jubilant New Zealand Warriors hoped their star Kevin Locke had escaped serious injury after his hat-trick inspired them to a 20-18 National Rugby League (NRL) win over the Sydney Roosters in rain-soaked Christchurch today.

In what Warriors fullback Lance Hohaia described as the coldest match he'd ever played - on either side of the Tasman - Locke's try from a kick and chase in the dying seconds, and James Maloney's goal from in front, handed them an unlikely victory after the Roosters led 18-8 with six minutes left.

But it left Locke writhing in agony, clutching his hip after he slammed into the upright in beating the Roosters' chasers to the ball. As Maloney added the extras, the diminutive winger was carted off AMI Stadium on a buggy but still managed a wave to the roaring crowd of 20,721.

"I know he's pretty sore; he's in hospital being assessed and we won't know until later on tonight or tomorrow," said Hohaia, who created the matchwinning try with a grubber for Locke.

"It (the final move) was planned; we were setting up for a play like that the tackle before and Kevin was right there. He never gave up the chase, he's a little speedster and he got there. We're really happy for him and hopefully the injury isn't too severe."

Locke, who was dropped mid-season by coach Ivan Cleary, put in a man-of-the-match performance with two first half tries; the first when he chased a Maloney kick 55m within centimetres of the dead ball line and the second just before the break from an error from Roosters fullback Anthony Minichiello.

Giant winger Manu Vatuvei gave the Warriors hope with the Roosters seemingly set for victory when he crashed over out wide in the 74th minute, and Maloney's sideline conversion got them within striking distance.

It was a welcome turnaround for the Warriors who had won just one of their previous nine matches in New Zealand outside Auckland, as the Roosters chose to take their home fixture to Christchurch.

Both sides were coming off the bye and the result gave them identical 7-7 records as the Warriors snuck into the top eight.

"We're pretty stoked I guess. We didn't do ourselves a lot of favours throughout the game. I'm pretty happy that we stuck in there and were able to come away with two points in pretty wretched conditions," Hohaia said.

"Besides playing in the UK, this is definitely the coldest weather I've had to play in. It does have an effect on you but there are 25 other players out there dealing with the same thing. We played tough for most of the game and we're very thankful to go home with the win."

Heavy rain on top of a hard surface made it difficult for both sides to keep their footing and the handling errors increased throughout the match.

The Sydneysiders suffered a pre-match setback when captain Braith Anasta, who had been shifted to lock, was ruled out with a hamstring injury and replaced by Wellingtonian Mose Masoe.

The Roosters led 12-8 at halftime, with five-eighth Todd Carney a dominant presence, and looked to have broken the game open thanks to former Kiwi Shaun Kenny-Dowall in the 64th minute.

Kenny-Dowall busted the line from inside his own half, then in the same set of six grabbed the ball 10m out and bulldozed over, carrying three Warriors defenders with him.

Carney's goal extended the lead to 10 points with 15 minutes left and it seemed a long road back for the Warriors in the conditions.

NZ Warriors 20 (K Locke 3 M Vatuvei tries J Maloney 2 goals) Sydney Roosters 18 (T Carney S Kenny-Dowall M Pearce tries T Carney 3 goals)

- NZPA