Mawson had been due to start their 0-0 draw at FA Cup opponents Sheffield Wednesday but was ruled out after picking up a knee problem.
And the Swans are now hoping the injury will not prove to be serious.
“It is something Alfie has felt in the past – he locked his knee," explained boss Carvalhal.
“It happened again today in the warm-up. In the past, after one or two minutes, he has felt okay.
“But today his knee stayed locked so there was no chance he could play.
“The good news is that after the game he said it was feeling much better, so let's see.
“We will find it in the next 48 hours, but I don't think it will be a big, big problem."