The 37-year-old Visnovsky, a key veteran presence to the team's blue line, took an accidental blow to the head and had to be helped off the ice during the first period of play. He will be re-evaluated on Sunday.
"To lose a guy that logs 20-plus minutes, that hurts you," Capuano said, according to Newsday's Arthur Staple.
Visnovsky, who averaged over 22 minutes per game for the Islanders, could require a stint on injured reserve. If he is expected to miss significant time, the team could look to unsigned free agent Radek Martinek. Martinek, who has played for the Isles in multiple tours, joined the team in camp on a professional tryout though he does not have a contract.
In other news, the Islanders sent Brock Nelson down to Bridgeport of the American Hockey League, though it is not immediately clear how long the assignment will last.