De Jong picked up the injury on international duty at the 2026 FIFA World Cup with the Netherlands and Barca are unhappy with their handling of the former Ajax playmaker in North America.
Barca requested De Jong return early from his summer break to check the extent of the injury and tests confirmed a tear - but De Jong is optimistic over a return to action in September.
That leaves a gap in Hansi Flick's midfield for the start of the campaign with Pedri, Gavi and Dani Olmo all still away on their post World Cup break as Fermin Lopez recovers from surgery.
Flick could turn to Marc Bernal as an option, after he was eased back into the squad last season, following an ACL injury in 2024, and the 19-year-old is ready to grasp the challenge ahead.
"I'm 100% ready. But the decision to play me will depend on the manager as he'll make the decision. But I see myself as a starter; everyone has to have confidence in themselves and what they can contribute to the team."
Barcelona kickoff their Spanish title defence on August 23 away at Elche.