A brilliant second-half defensive display earned Sydney Roosters a gutsy 13-6 NRL victory over the Warriors at ANZ Stadium on Saturday night.

The night was soured late when Roosters centre Shaun Kenny-Dowall and Warriors prop Sam Rapira left the match with potentially serious injuries.

Kenny-Dowall went down in the 66th minute with a high ankle sprain, before Rapira followed suit with a suspected broken wrist five minutes later.

Despite not scoring a point in the second half until five-eighth Todd Carney's 78th minute field goal, the Roosters were able to get their season back on track thanks to a stonewall defensive effort in the final 30 minutes.

The Warriors had plenty of chances to level the scores, but the Roosters' desperation on their goal line proved the difference in the end.

The home team took a 12-0 halftime lead thanks to a frantic final five minutes in which Kenny-Dowall and back-rower Aidan Guerra crossed after the match looked destined to be deadlocked at 0-0 as both teams played conservatively in rain-affected conditions.

The match featured a curious moment when Simon Mannering got the Warriors back into the contest to start the second half.

Mannering capitalised on an error from Roosters winger BJ Leilua, who failed to clean up a grubber from Warriors debutant Shaun Johnson in the 44th minute.

Mannering forced the ball and claimed a try, but Leilua then picked it up, and playing to the whistle raced 100 metres downfield to claim a try of his own.

Video referee Pat Reynolds ruled that Mannering had scored and flashed "TRY" on the big screen - much to the delight of the Roosters portion of the 10,116-strong crowd who thought the try had been awarded to Leilua.

Five-eighth James Maloney, who had a try of his own denied soon after, converted to cut the Roosters lead to six points and the Warriors looked to have the momentum, but were unable to trouble the scorers for the rest of the night.

Roosters coach Brian Smith credited a turnaround in attitude from his team, led by skipper Braith Anasta, in the wake of a disappointing 20-6 loss to North Queensland as the catalyst for the win.

"The decision that guys made on Saturday night, and certainly on Monday, after a disappointment in North Queensland and the way they responded to that is why we're sitting here with two competition points tonight, they were prepared to back that up," Smith said.

"I'll embarrass our skipper (Braith Anasta) by saying his leadership during the week in particular and at various stages tonight when we needed someone to do something extra special ... I thought he dug deep for us."

Kenny-Dowall went for scans immediately after the match, but officials were hopeful the injury was not as serious as first thought, and could sideline him for as little as two weeks, while Warriors coach Ivan Cleary said Rapira would be monitored but should be OK.

Cleary lamented the no-try to Maloney, which was denied by Reynolds for a knock-on from Krisnan Inu, but could not take anything away from the Roosters stoic effort.

"I just don't see how you could say that was a knock-on in one look, that is my opinion," he said.

"We've played worse than that and won (this year), you've got to give them some credit.

"I couldn't ask for any more from the boys."

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