Philippe Coutinho is set to miss Barcelona's trip to Juventus after suffering a hamstring injury, with the club confirming the full extent of the issue on Sunday.
Coutinho has re-emerged as a vital member of Barca's squad since returning to Camp Nou earlier this summer.
The Brazilian flopped in his first season at Camp Nou following a £142 million ($185m) move from Liverpool in 2018, and was subsequently sent out on loan to Bayern Munich.
He helped Bayern win a domestic treble last season, and even scored against his parent club in a stunning 8-2 quarter-final triumph in the Champions League, but the German outfit decided against bringing him in on a permanent basis.
Barca were tipped to sell Coutinho to an alternative suitor in the summer transfer window, but new Barca boss Ronald Koeman made it clear he still had a future at Camp Nou after replacing Quique Setien in the managerial hot seat in August.
The Dutchman has since been rewarded for his faith in the 28-year-old, who has contributed two goals and two assists in six appearances for the Blaugrana at the start of the 2020-21 campaign.
Coutinho has been arguably Barca's most consistent performer over the past two months, but he allowed his standards to dip during Saturday's Clasico clash against Real Madrid.
The former Liverpool star played the full 90 minutes of the 3-1 home defeat, with goals from Federico Valverde, Sergio Ramos and Luka Modric rendering Ansu Fati's effort for the hosts as nothing more than a consolation.
Barca have now revealed that Coutinho has picked up a knock which could see him sit out a midweek encounter with Juve in the Champions League, but have not been able to offer a firm return date for the midfielder.
❗ MEDICAL ANNOUNCEMENT
— FC Barcelona (@FCBarcelona) October 25, 2020
▶ @Phil_Coutinho has left hamstring injury
🔗 https://t.co/bOYtInquKU pic.twitter.com/YH8aZfe7oB
"A test on Sunday morning has revealed that Philippe Coutinho has a left biceps femoris (hamstring) injury. Exactly how long that means he will be out of action depends on how the injury evolves," a statement on the club's official website reads.
"Coutinho started Saturday’s Clasico and played the full ninety minutes, and has appeared in a total of six competitive games thus far this season (five in La Liga and one in the Champions League), scoring one goal in each competition."
Barca will have to avoid a defeat at the Allianz Stadium to remain top of Group G, having won their opening game of their European campaign 5-1 against Ferencvaros on Tuesday.