"I won't go into any details, but it's pretty serious," coach Lindy Ruff said, according to several American media outlets.
Kulich has missed the last three games due to illness, writes the AP news agency. Buffalo coach Ruff expects the Czech to play more this season, but that it will only be a few weeks before there is a forecast for when a comeback might happen.
The 21-year-old center is in his second full season with Buffalo and has three goals and two assists in 12 games this season. Last season, he had 24 points in 62 games.
