"It's encouraging to know Kevin came through the full 80 minutes for the Vulcans last weekend," said Warriors head coach Brian McClennan.
"He'd had next to no football for more than two months so it was important that he was able to play a full game.
"Once again it's a tough time for Sam. He was just getting back into his work after time out with an ankle injury and now he's out for a long time. It's so disappointing for him but Steve has been working his way back, getting minutes in for the Vulcans and he's ready now to come back into the NRL."
The tough-tackling younger Rapira, 23, missed the start of the season with a serious ankle injury he received in the Warriors' trial against South Sydney in Coffs Harbour in February.
He had to wait until May 12 for his comeback, appearing for the Vulcans against Windsor; since then he has played for them against Canterbury-Bankstown, Cronulla and Newcastle.
Locke played the first four games of the year before leaving the field with a leg injury late in the encounter with Gold Coast on March 24.
He returned against Melbourne on Anzac Day but lasted just six minutes before being forced off with a sternum injury.
Monday night's match - Queen's Birthday in Australia - will kick off at the earlier time of 5.30pm local time (7.30pm NZT).
Warriors: Kevin Locke, Bill Tupou, Ben Henry, Konrad Hurrell, Manu Vatuvei, James Maloney, Shaun Johnson, Russell Packer, Alehana Mara, Ben Matulino, Elijah Taylor, Simon Mannering, Feleti Mateo. Interchange: (from) Lewis Brown, Steve Rapira, Sione Lousi, Jacob Lillyman, Glen Fisiiahi