He will at least miss Saturday night's blockbuster clash with ladder leaders Geelong and the following week's meeting with reigning premiers Sydney Swans.
Thomas consulted a specialist on Thursday afternoon after leaving the training track early on Wednesday.
"The medical opinion is that if Dale has his training scaled back, the load-bearing work reduced for a couple of weeks, then the ankle should settle and he will be able to resume full training," Collingwood football director Geoff Walsh said.
There has been contention over the injury after post-season surgery was delayed while Thomas travelled overseas, in part for a sponsor's promotion.
It's the same ankle that plagued the Collingwood midfielder through the pre-season and delayed his start to the year.
Earlier this year out-of-contract Thomas went on record saying he didn't want to discuss his future with the Magpies until he was back to full fitness.
As it stands, talks have still not begun.
"We really haven't had the chance to get some clear air," Walsh told AFL.com.au.
"Obviously at the time we were wanting Dale to get back and get playing some footy, he's only just started to do that, then this happened," he said.
The 25-year-old is one of the highest profile players on the restricted free agents' list.
Matt Thompson is a reporter for AFL Media. Follow him on Twitter @MattThompsonAFL
