North Queensland are steeling themselves for a two-week reality check, with games against Manly and premiers St George Illawarra to determine the merit of their recent run of good form.

The Cowboys secured their first three-game winning streak since June 2009 when they defeated an injury-hit Cronulla 30-12 at Toyota Stadium on Saturday night, co-captain Johnathan Thurston playing a commanding role in the dominant win.

The victory left the Townsville-based side just one win behind ladder-leaders Brisbane, yet despite the Cowboys being the only side in the NRL to beat the Broncos and Melbourne this season, there are plenty still doubting their premiership credentials.

Even the Cowboys players themselves seem unsure as to their standing as competition challengers, with a testing upcoming fortnight to provide the answer to several questions.

"We haven't had a win (at Cronulla) for a while so we're travelling ok, we've just got to keep preparing well and the true test will come over the next couple of weeks when we play Manly who are going really well and obviously the Dragons who have been going really well the last couple of years," Thurston said.

"That will certainly test us."

And nowhere will they be tested more than at the defensive end, which has become a new strength for the Cowboys after leaking a league-worst 667 points in 2010.

Their defensive line stood firm against a mountain of Cronulla possession o Saturday night, young five-eighth Ray Thompson symbolising the new-found desperation within the side as he continually put his body on the line attempting to stop Sharks skipper Paul Gallen.

"It's been a focus for us and it had to be on last year's poor defence and how many points we conceded," coach Neil Henry said.

"We've let ourselves down a couple of times this year but we know we can keep building on performances like that (against Cronulla) and with Manly and St George coming up the next two weeks you're going to have to be solid defensively against sides like that too.

"It's a hard place to come to Shark Park and we haven't had a lot of success here, but to the boys' credit tonight was an outstanding game."

Not so outstanding were the Sharks, who failed to recover from the twin injury blow of losing Nathan Gardner and Albert Kelly.

Both will be assessed early this week, Gardner hoping his injury is nothing more than an ankle sprain while scans are expected to confirm Kelly will miss up to two months with a broken leg.

Gallen said the team had to adapt better to adversity, with the game there to be won midway through the second half.

"We're right in the game and then something goes wrong and we're just lacking a bit of self belief, just to hang in there," Gallen said.

"It doesn't matter about the injuries ... we just didn't believe that we could win it."

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