Barcelona currently have four players in their treatment room: De Jong, Roony Bardghji, Joan García and Andreas Christensen.
The Dutch midfielder has been out the longest, since suffering a medial collateral ligament tear in his right knee during this summer's World Cup, but his recovery is following the cautious timeline the club set out, and the plan is for him to rejoin the squad once the international break ends.
De Jong opted for conservative treatment over surgery, against the wishes of some inside the club, though Hansi Flick and Barcelona ultimately backed his decision.
He explained in an interview with Marca last month how the injury worsened after he was initially cleared to keep playing: "Someone fell on me in training.
"I had tests done and it turned out there was a small problem in the knee, and they told me I could carry on playing, that I would have some pain, but that I could keep going. They assured me it couldn't get worse.
"But then I had another test done and it showed the injury was now more serious than when I first got it in the United States. It was very tough because I wasn't expecting it. I'm really screwed over by this."
His progress is being managed carefully, with the plan to gradually increase his workload over the coming days, including ball work in some sessions, so he can rejoin full training after the break, though no firm return date has been set.
The club remains cautious given the risk of a setback, and De Jong's reintegration is expected to be gradual given how long he has been without match rhythm. Competition for a midfield place will also be significant: the 29-year-old, one of Barcelona's captains, faces competition from Pedri, Rodri, Marc Bernal and Gavi for a starting spot.