Louis Thompson has suffered a double fracture to his fibula.
Danny Cowley confirmed the news after visiting the stricken midfielder at QA Hospital on Saturday evening.
Thompson was stretched off the pitch during the first half of a League One victory over Bristol Rovers at Fratton Park following a challenge by Glenn Whelan.
He is now set for a spell on the sidelines, although Cowley is hopeful that the injury is not as bad as it might have been.
"It’s a double fracture to the fibula, which is the non-weight-bearing bone in the leg. That’s a positive because the tibia is a more serious injury."
The Blues boss said: “We want to thank doctors and nurses at QA Hospital for the brilliant way they treated Louis – they’re real life superheroes.
“We also want to thank the medical staff at ground. We’re so grateful for all of their work and I know Louis feels exactly the same.
“It’s a double fracture to the fibula, which is the non-weight-bearing bone in the leg. That’s a positive because the tibia is a more serious injury.
“We don’t quite know the extent of the damage just yet, though. Louis will have an MRI scan and then we’ll know more, but we’re hopeful it’s not as bad as we first feared.
"I just want to thank the nurses and doctors at QA Hospital" 🙏
— Portsmouth FC (@Pompey) August 22, 2022
🗣️A message from #Pompey boss Danny Cowley pic.twitter.com/3gAZmRfIWf