Hearts could be without Calum Elliot until Christmas after the striker underwent knee surgery.
Elliot, who scored four goals in four games at the start of the season, had the operation on Wednesday, his 24th birthday.
"They're talking round about six months," said manager Jim Jefferies. "It's a blow for the boy and the club. He's been plagued with injuries a lot.
"We'll do everything we can to get him back as quick as possible."
There was more encouraging news on Kevin Kyle, with the striker poised to resume training after a double hernia operation.
Jefferies added: "He's going to train today. He's doubtful for the next couple of days.
"It's a lot better, it's settled down. The only test will be when he starts training.
"If there's no reaction it's good news."
Hearts' squad is decimated by injury and suspension ahead of Sunday's Edinburgh derby with Hibernian at Easter Road.
Defender Eggert Jonsson and midfielder Adrian Mrowiec are banned, while Lee Wallace is a major doubt after recent ankle trouble.
Winger Suso Santana and midfielder Rudi Skacel are doubtful, and captain Marius Zaliukas will be assessed on Thursday after returning from international duty with Lithuania.
Jefferies added: "We've had to handle it over the last few weeks. It's not been ideal.
"Maybe that's one of the reasons we've not been at our best, but what a great time to get good form back on Sunday."