The Irishman has not travelled with Ally McCoist's squad to their Highland training camp this week after continuing to struggle with a knock picked up last season.
Boss Ally McCoist hopes the injury won't prove too serious as the 31-year-old looks to get himself fit for the new Championship campaign.
He said: "Jon has been feeling his knee over a couple of days in training and he felt it towards the end of last season as well.
"He is going for a scan and once we get the results we'll be in a better position to give more information.
"Our view last season was the problem was fatigue more than anything and that a rest would let him come back fresh and raring to go.
"That was the case at the start of pre-season, but after two or three days he felt a niggle.
"Our physio Stevie Walker and the doc felt a scan was the best idea to put everyone's minds at rest and hopefully it's nothing too serious."
Daly is not the only absentee from the Gers group, with Arnold Peralta and Bilel Mohsni given extended leave and David Templeton added to the crock list again.
McCoist said: "Temps went over on the ball last week at Murray Park and had a twinge at the back of his knee.
"He didn't train on Friday, Saturday or Monday so we decided to leave him behind.
"He's been getting a little bit of treatment and now he's joining in and doing the work the lads did which he has missed with Jamie Ramsden and Gordon Durie.
"David will hopefully be at the same level of fitness by the time we go back down the road and he can join in with us in the week before we go to America."