Hearts have learned the extent of Jamie Walker's hamstring injury after sending him for a scan.
The attacking midfielder is expected to be out for around three weeks with the problem, which he sustained against Rangers on Saturday.
Scans have confirmed a strain which rules the 24-year-old out of the club's next two matches at least. It is another setback to the Tynecastle manager Craig Levein as he copes with a midfield injury crisis.
Already without Arnaud Djoum, Don Cowie, Prince Buaben, and Malaury Martin, losing Walker is a major blow to Hearts. They face Kilmarnock at BT Murrayfield on Sunday and are scheduled to return to Tynecastle two weeks later to play Partick Thistle.
Walker won't feature in any of those fixtures and is now racing to be fit for Ross County's visit to Edinburgh on November 25.