Heart of Midlothian are due to discover the severity of Barrie McKay's knee injury.
The playmaker sustained an injury at the end of the 1-0 win over Hibs at Easter Road last month. He limped from the pitch at full-time after receiving treatment.
McKay had already missed a chunk of the season due to recovery from an ankle issue over the summer before suffering a knee injury at the end of August in the Conference League play-off against PAOK.
Naismith confirmed the issue is the same knee but "not specifically the same injury" which kept him out for three months.
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"We will hear some feedback from his scan on the 4th or the 5th [of January]," he said. "We will find out then what the timescale is for it. Everybody seems to be thinking that it is not as serious as before. That’s the indication we’ve got but we will wait and see what the specialist says."
Speaking last month, McKay noted the injuries this season as being "quite freak".
"Since I've come to Hearts I've never been injured," he said. "I've never experienced it before so I have been quite lucky. To get two relatively bad ones straight after each other is probably quite freak. You need to deal with it, it is the risk you take as a footballer that there is always a chance you can get injured.
Meanwhile, Beni Baningime missed the second match in a row when he was absent from the win over Livingston. His presence was missed in the 2-2 draw with Ross County three days prior.
The midfielder, like McKay, also received treatment toward the end of the derby.
"He was feeling fatigued and he was really knackered after the last game [win over Hibs]," Naismith explained. "He had a wee feeling in his knee and especially with the surface, I wasn’t willing to risk him."
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