Matthews is active Sunday against the Eagles.
Matthews is expected to play with a club on his right hand after missing four games with a thumb injury.
He's now missed four straight games with a thumb injury.
McCarthy said Matthews may have to play with a cast when he returns. He says it could be "multiple weeks" overall. Matthews was hurt last weekend against the Lions. He has also been bothered by a sore hamstring.
Matthews sacked Matthew Stafford on the last play of the quarter on a third-and-9 at the 34 to push the Lions out of field-goal range. He jogged to the locker room with a trainer and did not return.
Matthews drew a personal-foul penalty in the 49ers' 34-28 win Sunday after he tackled Kaepernick out of bounds deep in Green Bay territory in the second quarter.
Matthews, who was drafted out of Southern California in the first round (No. 26 overall) in 2009, is the only player in franchise history to be named to the Pro Bowl in each of his first four seasons. He has 42.5 sacks and has finished in the top five in sacks two of the last three seasons (13.5 in 2010, 13 in 2012).