Thompson left the field in the second quarter with a knee complaint and didn't feature for the rest of the afternoon in what was just his third game back from multiple knee reconstructions.
The 31-year-old ruptured his left ACL in 2019 and partially tore his right in 2020, leaving him sidelined for all of 2019, 2020 and 2021.
Following Gold Coast's 19-point loss, Dew remained hopeful that Thompson's injury wasn't serious.
"We're not fearing the worst," Dew said.
"It's obviously a knee injury, but at this point we think it's not the worst case. We'll have to wait and see.
"We feel for Rory. He's been integral since he's come back in and makes players better around him."
Thompson will undergo scans on Monday, with the club expecting the defender to be diagnosed with a meniscus injury, per reports from the Herald Sun's Jon Ralph. That would see Thompson sidelined anywhere between 4-12 weeks.
Gold Coast expects Rory Thompson to be diagnosed with a meniscus injury after scans tomorrow. No ACL issues. But could be anywhere between 4-12 weeks depending on the severity. Mac Andrew close but not yet the next cab off the rank https://t.co/6ADmWCRkcn
— Jon Ralph (@RalphyHeraldSun) May 22, 2022
Thompson wasn't the only Sun to go down on Saturday afternoon, with fellow defender Jy Farrar ruled out with concussion.
"I haven't had a heap of time to check on Jy but that's (a standard concussion) the information so far," Dew said.
"Credit to our guys. I think for all the second half we were down one.
"Our guys will take a lot of goodness out of that in terms of the fact that they were able to fight on under duress, and keep coming."
Under the AFL's concussion protocols, Farrar will miss Round 11's clash against Hawthorn.