"No one is safe. We want performances on the field so we need competition [for spots] to guarantee that. When people slip up, I need to make changes. The players are aware of that and that drives performance.
"Errors are really hurting us at the moment and I need to keep the players accountable to that."
Faitala-Mariner played for the Junior Warriors in the 2013 NYC grand final before joining the club's fulltime NRL squad last year. He was a fixture of the Warriors' NSW Cup side last season and figured in the club's NRL trials against the Titans and Penrith in February.
He has been on the cusp of selection this season and last weekend travelled to Townsville as the NRL side's 18th man.
Rapira has played three games for the NSW Cup side since recovering from a hamstring injury. He moves to the English Super League next year.
"Sam would have been picked in round one and he's really starting to hit some form," McFadden said. "We're changing up the dynamic of our bench. Dam has done well but need to play some footy."
The club's first-ever Anzac Day match at home launches a programme of five games in five cities on a day New Zealanders and Australians unite to commemorate the 100th anniversary of Gallipoli.
Warriors side to play the Titans at Mt Smart Stadium on Saturday (1.45pm): Tuimoala Lolohea, Jonathan Wright, David Fusitu'a, Solomone Kata, Manu Vatuvei, Chad Townsend, Shaun Johnson, Jacob Lillyman, Thomas Leuluai, Ben Matulino, Bodene Thompson, Ryan Hoffman, Simon Mannering (c). Interchange (one to be omitted): Nathan Friend, Raymond Faitala-Mariner, Sam Lisone, Sam Rapira, Dominique Peyroux