A knee injury has badly disrupted the defender-turned-striker's season so far but he was able to pull on his boots for the youth side's clash with Central Coast Mariners.

Harnwell played 45 minutes of the 1-0 win before being replaced by another experienced performer, Eugene Dadi. 

Dadi took advantage of some great lead-up play from Todd Howarth to head home the winner at the back post in the 77th minute.

He might have put Perth in front before that but his close range header on the hour was straight at Mariners goalkeeper Andrew Redmayne.

"It felt really good. The last couple of weeks I've been getting twinges but they have reduced and I got through 45 without any twinges and more importantly without even thinking about it," Harnwell told Perth Now.

"Even though I was confident, when you get out there you're never quite sure, so that was good to get through."

Both Harnwell and Dadi could come into the frame for Perth's next A-League clash, a home encounter with Brisbane Roar on Sunday.