The Queensland forward is expected to miss at least three weeks after the club confirmed he picked up a foot injury during Sunday's game against the Gold Coast Titans.
While Flegler will begin rehabilitation on a lisfranc injury in his foot, it could go from bad to worse for the Broncos if he requires surgery.
This could see him miss the remainder of the season as seen by Bulldogs forward Luke Thompson. Thompson required surgery on the same injury before the season began and is yet to play a single game this season.
"Fleg has a lisfranc injury in his foot, and again we will see a specialist in coming days to decide on the best option for treatment," Broncos Head of Performance Dave Ballard said.
The club has also issued an injury update on back rower Jordan Riki.
Riki is facing at least six weeks on the sidelines but could potentially be the remainder of the season due to a plantar fascia problem.
“Jordan has sustained a plantar fascia injury and stress reaction and we will consult a specialist this week to map out a way forward,” Ballard added.
“Both players will miss this weekend's game and we will take on board the medical advice before sorting out what the weeks ahead look like in terms of rehab for Jordy and Tom.”