The Bayern Munich loanee, who has yet to impress since joining the Welsh outfit last summer, sustained the damage during last month's FA Cup tie against Notts County.
Carvalhal is confident that Sanches will be back in contention in the coming weeks, however, rather than missing the majority of the campaign as initially feared.
"He is progressing. In the beginning, they said it could be long-term, but I believe he will come back next month," he told the club's official website. "That's my feeling. I think he will be back sooner than we expect."