Hearts fear over John Souttar injury
Hearts fear a long-term injury to defender John Souttar as they prepare to sign midfielder Alexandros Tziolis and striker Esmael Goncalves.
Souttar was stretchered off during Sunday's 4-0 defeat by Celtic.
Hearts head coach Ian Cathro said: "Right now it is a worry. It is a concern surrounding his Achilles."
He confirmed interest in Anorthosis Famagusta's Goncalves and Greek international Tziolis, who has left PAOK Salonica in his homeland.
"It has already been spoken about, probably from the other end, in the case of Goncalves, and Tziolis is now a free agent," said Cathro.
"We are working on both of those things. It is possible, but there is still a little bit of work to be done."
The 31-year-old Tziolis, who has played for Panathinaikos, Werder Bremen and Monaco, has been capped 62 times for his country but left PAOK after failing to make an appearance this season for the Greek Superleague club.
Goncalves had a loan spell in 2013 with St Mirren from Portuguese club Rio Ave, where Cathro was assistant.
The 25-year-old is presently with Anorthosis Famagusta and has made 21 appearances for the Cypriot First Division club this season after leaving his native Portugal.
"We need to bring people," said Cathro. "As it stands, we are short and we need to bring more players, guys who bring different qualities, guys who bring us more strength and competition and options."
Sunday's injury to Souttar could force a rethink of his signing plans ahead of Tuesday's January deadline.
"There was a challenge and then he landed awkwardly," said the head coach. "There is a bit of concern just now, it is an Achilles issue.
"We don't know the extent of it. But, as you saw, it didn't look nice.
"It will be in the next few hours and tomorrow morning before we know exactly what it is."
Cathro has already made six signings during January, with on-loan Stoke City winger Moha Choulay making his debut against Celtic from the bench and former Stirling Albion striker Dylan Bikey an unused substitute.
Hearts have only won twice in eight games since Cathro took charge, but he insisted he saw signs of promise despite the scoreline against the Premiership leaders.
"We should feel strong about some of the things we've done today, there's a lot of positives and I think the game was very close to swinging the other way," said Cathro, who thought his side paid for a second-half miss by Malaury Martin when Celtic were 1-0 ahead.