Barcelona goalkeeper Neto is facing a spell on the sidelines after fracturing a bone in his left wrist.
The 30-year-old arrived at Camp Nou from Valencia during the close season in a deal worth up to €35million.
With Jasper Cillessen moving the opposite way, Neto was brought in to provide competition for Marc-Andre ter Stegen.
But Ernesto Valverde now faces being without his back-up keeper for the opening stages of the season as he picked up an injury in the final training session ahead of Saturday's friendly against Napoli.
Barcelona announced on their official website that Neto has been diagnosed with a scaphoid bone fracture and the extent of the injury will be determined on Monday.
Reports in Spain suggest the Brazilian, who featured in Barcelona's first four pre-season matches, is likely to miss five weeks of action.
The Spanish champions begin their LaLiga campaign with a trip to Athletic Bilbao next Friday and face Real Betis and Osasuna before the end of the month.
Lionel Messi is also doubtful for the start of the season because of a calf strain.