Ousmane Dembele could miss up to three weeks after pulling his hamstring just 25 minutes into his full Barcelona debut in La Liga, Marca have reported.
The French winger was forced to withdraw in the first-half as his side went on to beat Getafe 2-1, with a late goal from fellow summer arrival Paulinho.
A club statement after the game read: "Ousmane Dembele has a hamstring injury in his left leg, more tests are needed to find out the extent of the injury."
Coach Ernesto Valverde echoed the statement, and admitted that losing the 20-year-old to injury so soon is "a shame".
"It's a muscle problem," he said. "We think it's a tear, but we will do more tests tomorrow.
"It's a shame because he was just getting up to scratch with the team's dynamic. We hope he won't be out for a long time."
Barcelona signed Dembele from Borussia Dortmund for an initial €105m, although it could rise to €145m with add-ons.
The youngster made his debut as a substitute in last weekend's 5-0 victory over Espanyol, providing an assist for Luis Suarez.
He then made his first start in Tuesday night's Champions League opener against Serie A champions Juventus.
"He's getting better in training all the time, but we'll see how he does competitively," Valverde said prior to his injury against Getafe. "We hope he's going to keep giving us more and more. You always ask about him, but we have to give him time."