"In my opinion, the situation is bad... Even if the treatment is non-surgical, return to full training will take at least about six weeks," Jacek Jaroszewski said in a news conference.
Team officials put off the decision on Glik's place in the squad until Thursday, when doctors from his club AS Monaco will decide on the treatment.
Earlier on Tuesday, the head of the Polish Football Association, Zbigniew Boniek, said he did not believe the 30-year-old would feature at the tournament.
"What bad luck, @kamilglik25 hurt himself, will not go to the World Cup," Boniek said on Twitter.
Glik got injured in training on Monday, shortly after Poland's coach Adam Nawalka had submitted his squad list to FIFA. If he is not able to recover, he will be replaced by VfB Stuttgart's Marcin Kaminski.
World Cup rules allow the final squad to be named 24 hours before the first game starts.
Poland play Senegal in Group H on June 19 before facing Colombia and Japan.
Before that, they play friendly warm-up matches against Chile on Friday and Lithuania next Tuesday.
(Reporting by Anna Koper,; Editing by Christian Radnedge)
