Hearts could be without Jamie Walker for up to a month after scans revealed the extent of his hamstring injury.
The attacking midfielder suffered the injury during the 3-1 defeat against Rangers at Murrayfield on Saturday.
It is another setback for manager Craig Levein as he is already without fellow midfielders Prince Buaben, Arnaud Djouma and Don Cowie through injury.
The only mitigating factor for Levein is that, after the game against Kilmarnock at Murrayfield on Sunday, they are not in action again until they host Partick Thistle on November 19.
That fixture is slated to take place back at Tynecastle, provided the delayed renovation of the main stand in Gorgie has been completed.