In his first seven appearances the rookie front rower has been used off the bench five times with his previous starts coming in the home wins against the Manly Sea Eagles and the Brisbane Broncos.
In 25 minutes on the field in last Sundays loss to Manly, Matagi made 71 metres from seven carries.
The move to start Matagi with Sam Rapira results in the Vodafone Warriors having two vastly-experienced props Jacob Lillyman (158 games) and Ben Matulino (128 games) to come into the contest from the bench.
The propping exchange is the only variation to the starting line-up initially named. The confirmed bench is Lillyman, Matulino, Todd Lowrie and Dominique Peyroux with Jerome Ropati 18th man. He was also 18th man against Cronulla and Manly.
It means the Vodafone Warriors will run with the same 17 players for the fourth game in succession.
With losses in the last two outings after a run of seven wins from eight games, the Vodafone Warriors take on Penrith on Heroes Day, the clubs annual celebration of the contribution the emergency services make to the community.
Following results so far this weekend, they go into their fourth to last match of the regular season in 12th spot on 22 points, just two behind eight-placed Gold Coast and ninth-placed Canberra, two sides they face in the next two rounds after the Penrith fixture.
The Panthers have remained on 20 points for four weeks having dropped their last four games to Newcastle (14-32), Cronulla (10-38), the Sydney Roosters (6-42) and North Queensland (4-36).
This will be captain Simon Mannerings 185th career appearance, drawing him level with Lance Hohaia in third spot on the Vodafone Warriors all-time list behind only Logan Swann (195) and Stacey Jones (261). Still only 26, Mannering will lead the side for the 85th time leaving him only six games short of equalling Steve Prices club record of 91 games in charge from 2005-2009.
VODAFONE WARRIORS v PENRITH PANTHERS
Mount Smart Stadium, Auckland
4.00pm, Sunday, August 18
Referees: Jason Robinson and Chris James
12SIMON MANNERING (c)
HEAD COACH: MATTHEW ELLIOTT