Gillet was stretchered off after just 37 minutes of ICT’s draw at Dunfermline to be replaced by Proctor, who was then injured himself by the hour mark.
Caley Jags gaffer Terry Butcher said the initial prognosis is far from encouraging and he expects to be without the pair for anything up to four weeks.
The injuries continue Inverness's appalling run of bad luck after our first season back in the top flight was blighted by lay-offs.
Tel told the Inverness Courier: “It didn’t look great for either of them on Saturday. I think we could be without them both for some considerable time.
“Add to that the fact Josh Meekings is still out with an ankle problem, then it’s three defenders we are going to have injured.
“I don’t know any other team in the SPL that’s had the problems we’ve had defensively because last season we also had a horrendous run with injuries.
“We had to change our back four three times against Dunfermline and to lose another two defenders to injury is a massive blow.”