Welsh international Owain Tudur Jones is to have surgery on Tuesday, with cartilage trouble confirmed, and the big midfielder faces a lengthy spell on the sidelines.
The new recruit from Norwich City, who made such a promising debut against Hibs which quickly earned him a recall to the Wales squad last week, is stunned at developments.
"Owain sustained a blocked knee against Rangers and it has been diagnosed as requiring a cartilage operation", said manager Terry Butcher.
"It's a massive blow to the lad and to the club as we're looking at a six to eight week layoff. But Owain is determined and he'll start his rehab right away."
Jones had made a positive impression and has shaped as capable of adding a physical presence to the Inverness midfield unit. But now he faces being on the sidelines until October.
Owain joins Lee Cox, Billy McKay, Josh Meekings, Kenny Gillet and David Proctor on the casualty chart
"That means we have six players out, which is a dreadful start to the season in injury terms", says Butcher."None of the five who missed the Rangers game will be back within a fortnight so the squad is fairly stretched.
"Add on Ross Tokely's suspension and we're looking at seven being out for Pittodrie, which is a challenge."
Though still looking for their first SPL win of the season, the team has been playing well and Butcher says: "We're getting rid of all our bad luck at the one time, what with injuries and being unlucky in matches.
"We played poorly for the first 45 minutes at Dunfermline, but since then we've performed well enough. That shows that we'll be fine. I'm certain that it will click in to a more positive scenario for us. "