The Brazilian played 80 minutes of Saturday's 3-1 defeat to Real Madrid in the Clasico, but produced an underwhelming display and the club have confirmed that he face a spell out.
The severity of the injury has not been confirmed, but the period of recuperation is likely to be up to a month, which could see Coutinho out of action until after the November international break.
The Frenchman was left on the bench completely for the midweek win over Ferencvaros, and was only given the last nine minutes of the Clasico.
Ronald Koeman has opted for Trincao and Pedri in these games and clearly wants to build his team around these young talents - but Coutinho being missing could give him an opportunity to play at No. 10 in the upcoming matches.