That shifts Javid Bowen to the wing and pushes Kalyn Ponga out of the side.
The confidence and form of halfback Chad Townsend is the Sharks' major concern after he was hooked against the Raiders.
He's sure to be sledged relentlessly by the Cowboys - in particular by Thurston.
Thurston's edge combination with Gavin Cooper will be crucial here.
The same goes for Thurston's relationship with Jason Taumalolo.
The Sharks can score points but they can scrap, too.
They will want a stop-start affair. The Cowboys, playing at a venue where they've lost six-straight games, will want a free-flowing match.
Key: The Sharks have to at least contain Taumalolo and his fellow Cowboys forwards if they are to triumph.
Tip: Sharks
Meanwhile, Storm coach Craig Bellamy and his opposite Ricky Stuart are good mates and often see eye-to-eye on football issues, but this is a match-up of competing rugby league philosophies.
This season's most miserly defensive unit Melbourne go head-to-head with by far the competition's greatest offensive team.
Ever since their preliminary final loss to North Queensland this time last year, the Storm, led by Cameron Smith and Cooper Cronk, have played with a steely determination.
The Storm's controversial ruck tactics are key to their suffocating defence, and Stuart has turned the spotlight on that this week.
But of even more concern to him will be his side's successive second-half fades.
Rain greatly helped the Storm in their qualifying final win over North Queensland, and if the heavens open again, - there's a 40 per cent chance of rain - they will be very hard to beat.
Like the Cowboys, Stuart's Raiders hope for an open game.
Bellamy wants the opposite.
The Raiders have youth on their side, but it's hard to see that being enough for the guile of Smith and Cronk.
The Raiders are unchanged after their win over Penrith.
Matt White will likely go in for the injured Nelson Asofa-Solomona (elbow) for the Storm.
Key: Leipana. If Canberra's slashing right-side combination of Joseph Leilua and Jordan Rapana can have the games of their life, the Raiders can win.
Tip: Storm
Preliminary finals
Tonight: Cronulla Sharks v North Queensland Cowboys at Allianz Stadium, 9.55pm
Head to Head: Sharks 24 Cowboys 16
Tomorrow: Melbourne Storm v Canberra at AAMI Park, 9.40pm
Head to Head: Storm 26 Raiders 11