Ousmane Dembele is set to miss "approximately five weeks" with a hamstring strain, Barcelona have confirmed.
However, the club confirmed Monday that Dembele has picked up a strain in his left hamstring, and will be out for around five weeks.
Dembele has enjoyed productive spells with the Liga champions since his move from Borussia Dortmund in the summer of 2017, but has often been limited by injuries.
A severe hamstring injury at the start of his time at Barca saw him miss over three months and he was sidelined for around another month with different muscle problem not long after his return.
Last season saw Dembele emerge as the preferred option in the Barca XI over Philippe Coutinho, but again he found himself sidelined with fitness issues at inopportune times.
An ankle injury last January knocked him out for three weeks and another muscle injury would sideline him for another month.
His latest injury concern comes at a difficult time for Barca, as their front line has been limited by fitness issues to start the season.
Lionel Messi was not risked in the Liga opener against Athletic as he recovers from a calf injury sustained during a shortened pre-season after his Copa America exertions with Argentina.
Luis Suarez went down with injury during the loss to Athletic, coming off in the first half with a calf problem of his own.
Barca can call upon new signing Antoine Griezmann, but have already moved on a pair of attackers from last season in Coutinho and Malcom this window.
Coutinho's exit to Bayern Munich was confirmed Monday, with the playmaker departing on a one-year loan deal with the Bundesliga champions holding a €120 million (£110m/$133m) option to buy at the end of the season.
Malcom departed the club earlier in the summer for a €45m move to Zenit, having spent one disappointing season with Barca after a dramatic transfer from Bordeaux last summer.