With Konrad Hurrell still working his way back to full fitness after wrist surgery, McFadden has placed 20-year-old Nines star Solomone Kata at right centre, with the more experienced Ngani Laumape on the left.
McFadden has big wraps on the speedy and powerfully built Kata but admits Laumape has the inside running to secure his position, ahead of Kata and new recruits Jonathan Wright and Matt Allwood.
"Sol's a pretty confident kid as well so I'm sure he'll take his opportunities. He's a real pocket rocket and he's a very big talent but he's still very young and we'll just see how he develops," he said.
"Ngani has had a fantastic pre-season. He turned up in great shape in November and he's really made some gains in his physical development.
"He had some really good games for us last year so he's probably going to get first crack at it. But his form has got to hold as well and we've obviously got some young kids that are chasing him."
Entering his third season in the NRL, Laumape has made no secret of his desire to find a permanent home in the midfield after previously featuring on the wing.
"Definitely in the centres," Laumape said of his preferred position. "I just want to go out there and play my best this weekend and hopefully all the hard work pays off. I'm on my preferred left side so I'm pretty happy.
"I'm looking forward to partnering Sol, he's a real good talent coming through."
Club captain Simon Mannering was not considered for the Geyer City clash, leaving Bodene Thompson to fill the second-row with Ryan Hoffman, while Ben Henry will start in the No 13 jumper.
With plenty of young forward talent included in the 24-man squad, McFadden hopes Saturday's game will help clarify who the genuine contenders are for back and front-row positions.
Warriors v Penrith
Rotorua, 3pm Saturday
Sam Tomkins
Ken Maumalo
Ngani Laumape
Solomone Kata
Tuimoala Lolohea
Chad Townsend
Shaun Johnson
Suaia Matagi
+Thomas Leuluai
Ben Matulino
Bodene Thompson
Ryan Hoffman
Ben Henry
Interchange: Matt Allwood, Marata Niukore, Api Pewhairangi, Sam Lisone, Nathaniel Roache, Sione Lousi, Raymond Faitala-Mariner, John Palavi, Albert Vete, Sam Rapira, Jazz Tevaga