Javier Mascherano will miss six weeks after suffering a medial ligament tear in Barcelona's 2-2 draw with Paris Saint-Germain.
Mascherano was stretchered off in the closing stages of the Champions League quarter-final first leg clash at Parc des Princes, with Marc Bartra coming on to replace him.
The club have since confirmed the Argentina international has suffered a ligament tear in his right knee, ruling him out of action until the closing weeks of the season.
Mascherano had picked up a yellow card earlier in the second half on Tuesday evening, meaning he would have been suspended from the clash at Camp Nou next week irrespective of his injury.
The news comes as a bitter blow to Barca as their injury problems continue to mount. Lionel Messi was withdrawn at half-time with a hamstring problem, while captain Carles Puyol is unable to play again this season after undergoing knee surgery last month.
A last-gasp Blaise Matuidi goal secured the draw in Tuesday's game, after Xavi's late penalty and Messi's first-half strike had seemingly secured a win for the Blaugrana despite a goal from Zlatan Ibrahimovic.