28-year-old centre Lafai and 33-year-old prop Graham are believed to have sustained syndesmosis injuries in the loss.
Dragons head of athletic performance Nathan Pickworth said the pair will need further medical evaluation.
“Tim (Lafai) has suffered a suspected moderate grade syndesmosis injury and will have follow up scans [on Monday],” Pickworth told the club’s website.
“James (Graham) suffered a similar injury to Tim and has a suspected syndesmosis injury with the possibility of a fibula fracture; he will have follow up scans to determine the severity of the injury and to hopefully exclude the fibula fracture.”
Meanwhile, 27-year-old second-row player Frizell will be evaluated for concussion after copping a heavy knock against the Sharks. The New South Wales State of Origin squad member will be evaluated by the Blues’ medical team ahead of game one in nine days’ time.
The Dragons have the bye this week, before returning to action against the Bulldogs at ANZ Stadium in round 13.