Costelow came off at half-time against the Springboks, while after impressing against Australia, Rogers had been named initially to face South Africa but was a late withdrawal from the starting side.
“Sam has picked up a bit of a head knock on the weekend, so he’s going through his head injury assessment (HIA) return to play protocols,” said Peel.
“Tommy [Rogers] isn’t right but I don’t think it’s a long-term issue, so we will manage him this week.
“It’s hopefully not a major problem, so we’ll see how he pans out, potentially for next week or the week after. We’re probably looking at that sort of time frame.”
Scarlets also had Eddie James, Blair Murray, Kemsley Mathias, Ryan Elias, Henry Thomas and Taine Plumtree in the Wales squad.
“The rest are available for selection,” said Peel.
“For us, it’s about welcoming them back into the fold. We’re proud of what they achieve as well when they go away.
“I get the results have been tough, but it’s about getting them back and quickly into what we’re trying to do.”
