Craig Levein confirmed that Ben Garuccio will miss the next ten months after the left-back tore his cruciate ligament in training.
The Australian has made 22 appearances in his debut season at Tynecastle Park but has been ruled out for the rest of the year following the injury news.
"We had a bit of bad news yesterday," Craig said. "Ben Garuccio has torn his cruciate in training so he'll be out for ten months or so. His foot got caught in the turf and twisted, just a complete accident. It's not good news."
With Garuccio injured and Demetri Mitchell ruled out until the end of the season it leaves Levein short on full-backs going into the crucial fixture with Aberdeen on Saturday, but the manager was still confident.
"It's a different occasion on Saturday. We're at home and there'll be a big crowd - Aberdeen always bring a fairly large support with them - and I think it'll be a smashing game."
It is the start of a brutal run of fixtures that sees the Jambos take on the Dons, Rangers, and Hibs in the space of a week.
"I'm not that keen on grouping things together - it dilutes the focus. Aberdeen is always a tough match and we can only deal with Aberdeen at the weekend, we can't deal with the games after that. If we get Aberdeen right then it'll give us some confidence going into the games that follow."
A win on Saturday could move Hearts to within two points of Derek McInnes' third-placed side as the race for Europe hots up. In recent weeks, Motherwell and Hibs have added their names to the list of sides who could qualify for the continent.
"I'm more concerned with Saturday's match and getting three points," Craig added. "We can all make noises. It's where you end up after the final game of the season that's important and there's still a long way to go."
You can watch all of Craig's press conference on HeartsTV by clicking here.