Craig Levein revealed to the Evening News that the 32-year-old had been suffering with a tight hamstring while with Scotland for their Euro 2020 qualifiers against Russia and Belgium during the past week.
It was the same issue which kept the player out the starting line-up of the 2-2 draw with Hamilton Academical at Tynecastle before the international break. The forward was brought off the bench just after the 80-minute mark as the home side chased the winner.
Naismith was forced to miss training on the eve of the Russia clash after the hamstring felt tight. The player was sent for a scan which "showed minor irritation".
Levein said: "The injury is nothing significant. He isn’t feeling the hamstring at the moment but to get him on the field we need to do a fair bit of work to make sure he is robust enough. The last thing I want to do is play him and have to take him off after 15 or 20 minutes.
"We will just follow the normal recovery procedure for the injury. If he doesn’t make this weekend, I’d be very confident he will make the following week."
With the nature of the problem and Naismith's recent history - he missed 22 games last season due to injury - it should be a case of not rushing him back, easing him in, until he is 100 per cent.
Yet, with an Edinburgh derby around corner, plus an important Betfred Cup quarter-final clash with Aberdeen, the club's poor form and the importance of the forward to the team there is an understandable desire to see him in the starting line-up.
Since the start of last season Naismith has started 28 times for the club, winning on 18 occasions. A win percentage of 64.3. In the other 29 games as a Hearts player he was unavailable or started on the bench there were just seven wins - three against lower league opposition. A win percentage of 24.1.
The contrast is both stark and slightly alarming, but one which they may have to adapt to during this campaign.
Levein's men have shown already this season that they are capable of coping in his absence. The best performance arrived at Motherwell in the Betfred Cup where the visitors deservedly came away with a 2-1 win.
At Fir Park, Hearts lined up 4-3-3 with Jamie Walker and Jake Mulraney supporting Conor Washington from the wide areas. In the midfield there was a nice balance in midfield as Sean Clare provided the power and directness, Andy Irving the control and brains and Loic Damour the muscle.
The away side were assertive and played at a tempo in keeping of what is expected of Hearts teams.
That being said, both goals came when the team had switched to a more conventional 4-4-2, Steven MacLean having replaced the injured Jamie Walker and Sean Clare shifting wide right.
Washington is clearly the first-choice striker for Levein with fans eager to see him lead the line with Naismith in a supporting role behind. It is clear to see that without Naismith, the Northern Irishman needs bodies around him.
Against Motherwell, MacLean's ability to drop deep to link play with midfield allowed Washington to stretch the game higher up the pitch. Against Accies he was often isolated and fighting a losing battle as he scampered and scurried around the final third. As for the Ross County game there was little chemistry with an off-the-boil Uche Ikpeazu.
In Sean Clare, Jake Mulraney and Ryotaro Meshino, there is an attacking trident with different qualities to play behind the summer signing. But there is also a lot of inconsistency, plus it is a big demand on Meshino to be required to hit the ground running.
That's why it may be time to turn back to MacLean and the attacking quartet which finished the first half so strongly against Motherwell last month.
The veteran forward has not been in the last two squads but he has the experience, the understanding and the responsibility to handle what is likely going to be a pressurised occasion on Saturday afternoon.
Levein needs to turn to guys he can trust and MacLean is one of those individuals. Starting along side Washington would send out a positive message to fans with two strikers on the pitch, plus an out-and-out winger in Mulraney with Clare on the right.
It should give the team a nice balance throughout. Clare will naturally play narrow and support Glenn Whelan and Irving, while MacLean will drop off the front and on to Liam Donnelly who has been such an asset for the Steelmen this year.
There has been a lot of doom and gloom around Tynecastle this year and the absence of Naismith adds to it. However, Hearts, as they have shown against Saturday's opponents already, are more than capable of getting their first league win at the fifth time of trying.
Three points will provide a positive step going into the Edinburgh derby at Easter Road where the club's talisman could well return.