While Cox has still contributed at stoppages, leading West Coast for hit-outs in the first two rounds, Worsfold said the four-time All-Australian was not having the desired impact around the ground.
The coach said Cox’s current fitness level was no excuse as he works his way back from extensive groin rehabilitation, but he was certain a change of form was around the corner.
“He knows where he’s at and you can see in his body language that he’s disappointed with the way he’s performed in the first two rounds", Worsfold said from Subiaco Oval on Wednesday.
“And I don’t really need to tell him that for us to be winning games we need him performing at his best - that's expected of every player.
“He’s determined to play better. Even with his current fitness level it’s no excuse not to impact the game when he’s on the field.
“If I thought he was just cruising along and not too concerned then I would be putting the acid on him, but I know how much it’s hurting him.”
Cox had seven possessions against the Brisbane Lions in round one from 63 per cent ground time and seven possessions in the round-two loss to Port Adelaide from 64 per cent ground time.
“We’re not using him out there as long, but when he’s out there he should still be able to have an impact on the game,” Worsfold said.
“His ruck work was really good, some outstanding ruck work on the weekend, but he’s not impacting around the ground, not judging the game as well as we know he can.
“He can’t quite make some of those contests at the moment, but that will turn around pretty quick.”
Meanwhile, three rookies are in contention to replace crucial defender Shannon Hurn, who has accepted a two-week suspension for a rough conduct charge.
Sam Butler (facial fracture) and Mark Nicoski (shoulder) have also been sidelined.
Andrew Strijk, Ashton Hams and Lewis Stevenson have impressed in the WAFL and, with Tim Houlihan (foot) placed on the long-term injury list, can be considered to face North Melbourne at Etihad Stadium on Saturday.
“They’ve all got the potential to come in and play that role,” Worsfold said.
“They’re not as good a kick as Shannon Hurn, but we believe they can come in and do a job back there.”
Will Schofield and Bradd Dalziell are also in form, the coach said and will be considered along with midfielder Matt Rosa, who has been sidelined with a back injury, and forward Ben McKinley.
Worsfold said Mark LeCras, who missed last week with hamstring soreness, was progressing well and was a chance to play against the Kangaroos.
However, dropped premiership player Quinten Lynch, who booted two goals for West Perth in the WAFL, did not contribute enough from full-forward.
“That’s an area we need to talk to Quinten about and West Perth about if Quinten wants to break back into our side.”
