The 27-year-old, who hasn't played in over a month after being hit by a puck while playing for HC Lev Praha of the KHL, is currently taking blood thinners.
"The doctors have to get that taken care of before he can be cleared to play," Feaster told the Herald. "He's not going to be cleared to participate. As far as when he gets here, when the doctors say he can play and whether he can fly -- we don't have answers to those things yet.
"But we expect to get them here in short order."
Cervenka is expected to take Olli Jokinen's role as the club's second-line center. Jokinen signed with Winnipeg in the off-season.
Meanwhile, with training camps set to open this weekend, the Herald reports the Flames will invite unsigned free agent center Steve Begin and defenseman Steve McCarthy to camp on professional tryout offers.