Griffiths did not feature for Celtic against Hearts in the Scottish League Cup semi-final tie on Sunday afternoon.
The 28-year-old Scotland international striker - who has been on the books of Celtic since January 2014 when he joined from Wolverhampton Wanderers for a transfer fee reported by The Daily Mail to be worth £1 million - is on the sidelines at the moment with illness and injury, as reported by The Scottish Sun.
Celtic, though, did not miss the former Dundee star, as Brendan Rodgers’s side got the better of Scottish Premiership rivals Hearts with ease.
After a goalless first half, Scott Sinclair put the Hoops in the lead on 53 minutes, before James Forrest and Ryan Christie found the target.
The Hoops will face either Rangers or Aberdeen in the final of the Scottish League Cup this season.
Celtic striker Griffiths has hit back at a Hearts fan on Twitter.
I didn’t no, but seems as though your team didn’t either. https://t.co/5JKRPRnM2C— LG9️⃣ (@Leighgriff09) October 28, 2018