The Portuguese midfielder was replaced after 32 minutes with a hamstring injury sustained during a Swans counter attack.
It has proved a frustrating month for the 20-year-old, who made his return from the same injury which saw him taken off at the same stage of the third-round stalemate at Wolves.
And it looks likely that he will sit out Tuesday night's clash with the Gunners, with Carvalhal hopeful of seeing him return for the trip to Leicester later in the week.
“He will be assessed after 48 hours," said Carvalhal. “Then we will know exactly what the problem is with him."