The pair began suffering from gastro on Saturday night and while both travelled with the team to Sydney, they were ruled out on Sunday morning, replaced by Steven Baker and youngster Tom Lynch.
With the Saints sitting in sixth place, just four points ahead of the Swans, the loss of the two key position players will give the home side a fillip in its quest to secure a top-eight berth.
The 20-year-old Lynch has been brought in for just his fifth game of the season, while Baker has been named substitute and will play his first match since round 13.
Gary Rohan, who has been sidelined since round four with knee and hamstring problems, has been named the Swans' substitute, with the recalled Nick Malceski, Craig Bird and Lewis Jetta starting on the bench.
