The Perth Scorchers' bid to land a home BBL semi-final has taken a hit with star paceman Jason Behrendorff ruled out of Saturday night's clash with the Melbourne Stars at the WACA Ground.

Behrendorff is no certainty to play again during this BBL campaign after suffering more soreness in his troublesome back.

The 25-year-old, cut down by a stress fracture in his back last summer, has experienced bouts of soreness since then.

He will be rested against the Stars on Saturday night in a bid to get him right for the finals.

The Scorchers will secure a top-two spot with victory over the Stars.

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But if the Stars manage to win by about 38 runs or within 15 overs, they will leapfrog the Scorchers into second spot.

So much is on the line, but both sides have been cruelled by withdrawals.

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The Stars are missing Australian ODI quartet Glenn Maxwell, John Hastings, Scott Boland and James Faulkner.

Perth are without Joel Paris, Behrendorff, Shaun Marsh and Mitch Marsh.

Behrendorff snared 15 wickets at an average of 16.73 to inspire the Scorchers to their second straight BBL title last summer.

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But the ongoing back injury was clearly affecting the left-arm paceman last week when he returned expensive figures of 0-45 in a win over the Hobart Hurricanes.

"His back's been sore for the past few games," Scorchers captain Adam Voges said.

"It just gets to the point where the pain is affecting his quality.

"We're hoping that by giving him this rest for this game, he'll be right for the semi-finals. But there's no guarantees."

Matt Dixon is set to replace Behrendorff in the side, with Jhye Richardson also in the frame.

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But while the Scorchers are already guaranteed a finals berth, the same can't be said for the Stars, who copped a 56-run hiding on Thursday night from the Brisbane Heat.

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The Stars will miss the finals if they lose to the Scorchers, and both the Thunder and Renegades win.

Perth Scorchers: Adam Voges (c), Ashton Agar, Cameron Bancroft, Travis Birt, Michael Carberry, Matt Dixon, Marcus Harris, Brad Hogg, Michael Klinger, Jhye Richardson, Ashton Turner, Andrew Tye, David Willey.

Melbourne Stars: David Hussey (c), Michael Beer, Jackson Coleman, Seb Gotch, Evan Gulbis, Peter Handscomb, Ben Hilfenhaus, Kevin Pietersen, Rob Quiney, Marcus Stoinis, Dan Worrall, Luke Wright, Adam Zampa