After scans on Monday morning, Rioli is confined to a moonboot and may not be available to play in any of Hawthorn's remaining three pre-season matches.
Rioli sustained the injury in the one-point loss to Gold Coast and didn't play in the Hawks second match against Brisbane Lions.
"Cyril rolled his ankle in the first game and pulled up a bit sore afterwards," Hawthorn football manager Mark Evans confirmed in a statement.
"He'll wear a moonboot for a couple of days to protect the ankle, and we expect he'll miss a couple of weeks," Evans said.
Scans also confirmed Paul Puopolo had not suffered anterior cruciate ligament damage after hyper-extending his knee in final moments of the loss to the Suns.
"At this stage a timeframe on his return is unknown, and we'll be guided by how the injury site settles."
Meanwhile, Western Bulldogs fans will be disappointed that Brian Lake won't line up against his old side at Etihad Stadium on Friday night to open round two of the NAB Cup.
The Hawks have confirmed he’s recovering from calf tightness.
"Brian tightened up a bit in the calf during the first game and won't play this week," Evans said.
"We'll see how he goes heading into the third round."
Matt Thompson is a reporter for AFL Media. Follow him on Twitter @MattThompsonAFL
